Use of peracetic acid/hydrogen peroxide and peroxide-reducing agents for treatment of drilling fluids, frac fluids, flowback water and disposal water

ABSTRACT

Methods for the use of peracid compositions having decreased hydrogen peroxide concentration for various water treatments, including oil- and gas-field operations, and/or other aseptic treatments are disclosed. In numerous aspects, peracetic acid is the preferred peracid and is treated with a peroxide-reducing agent to substantially reduce the hydrogen peroxide content. Methods for using the treated peracid compositions for treatment of drilling fluids, frac fluids, flow back waters and disposal waters are also disclosed for improving water condition, reducing oxidizing damage associated with hydrogen peroxide and/or reducing bacteria infestation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S.Provisional Application No. 61/617,814, filed Mar. 30, 2012, titled “Useof Peracetic Acid/Hydrogen Peroxide and Catalase for Treatment ofDrilling Fluids, Frac Fluids, Flowback Water and Disposal Water,” whichis herein incorporated by reference in its entirety.

This application is also related to U.S. patent application Ser. No.13/798,311, entitled “Use Of Peracetic Acid/Hydrogen Peroxide andPeroxide-Reducing Enzymes for Treatment of Drilling Fluids, Frac Fluids,Flow back Water and Disposal Water,” U.S. patent application Ser. No.13/798,307, now issued U.S. Pat. No. 9,242,879, entitled “Use OfPeracetic Acid/Hydrogen Peroxide And Peroxide-Reducing Agents ForTreatment Of Drilling Fluids, Frac Fluids, Flow back Water And DisposalWater,” and U.S. Patent Application Ser. No. 61/710,631, filed Oct. 5,2012, and titled “Stable Peroxycarboxylic Acid Compositions and UsesThereof,” each of which are filed concurrently herewith. The entirecontents of these patent applications are hereby expressly incorporatedherein by reference including, without limitation, the specification,claims, and abstract, as well as any figures, tables, or drawingsthereof.

FIELD OF THE INVENTION

The present disclosure relates to percarboxylic acid compositions andmethods for the use of peracid compositions with decreased hydrogenperoxide concentrations for various water treatments, including oil- andgas-field operations, and/or other aseptic treatments. The presentinvention also relates to slick water compositions and gel basedcompositions that comprise stable percarboxylic acid compositions andthe use thereof in oil- and gas-field operations. In numerous aspects,peracetic acid is the preferred peracid and is treated with aperoxide-reducing agent, such as a metal or strong oxidizer, tosubstantially reduce the hydrogen peroxide content. The methods oftreatment are particularly suitable for treatment of drilling fluids,frac fluids, flow back waters and/or disposal waters for improving watercondition, reducing oxidizing damage associated with hydrogen peroxideand/or reducing bacteria infestation.

BACKGROUND OF THE INVENTION

Peroxycarboxylic acids (also referred to as peracids), as well as mixedperoxycarboxylic acid systems, are known for use as antimicrobials andbleaching agents in a variety of industries. Peracetic acid orperoxyacetic acid (PAA or POAA) (dynamic equilibrium mixture ofPOAA/PAA, H₂O₂, H₂O and AA) have been used in the food and beverageindustries as a fast acting, “green” antimicrobial. Such productsdemonstrate beneficial properties towards oxidizing solids and improvingwater quality. In addition, compared to other commercially availablebiocides, the use of peracetic acid results in a low environmentalfootprint due in part to its decomposition into innocuous components(e.g. acetic acid (AA), oxygen, CO₂ and H₂O). See for example, U.S. Pat.No. 8,226,939, entitled “Antimicrobial Peracid Compositions withSelected Catalase Enzymes and Methods of Use in Aseptic Packaging,”which is incorporated by reference in its entirety.

Peracids have also been used for certain water treatment applications.However, these have been very limited in the area of commercial welldrilling operations. See for example U.S. Patent Publication No.2010/0160449, entitled “Peracetic Acid Oil-Field Biocide and Method,”and U.S. Pat. No. 7,156,178 which are incorporated by reference in theirentirety. However, particular water treatment applications presentdifficulties for the use of peracids during several steps of the oil andgas production methods, including for example microbial efficacy andcompatibility concerns. For example, despite its fast action andeco-friendly properties, the use of peracids, including peracetic acid,has a number of limitations for use in water treatment methods. Highdosages of the peracid can increase the corrosion rates in pipelines andequipment due in part to the presence of hydrogen peroxide (H₂O₂).Moreover, the peracids/H₂O₂ can interfere with the activity offunctional agents necessary for the methods of water treatment in oiland gas recovery, including friction reducers and thickeners which areoften critical for the fracking process. In addition, peracids andhydrogen peroxide are prone to quenching from common, naturallyoccurring chemicals which can severely limit their utility.

There remains a need for enhanced water treatment methods. For example,from a microbiology perspective, mitigation of microorganisms isessential to minimize environmental concerns for waste products and toavoid contamination of systems, such as well or reservoir souring and/ormicrobiologically-influenced corrosion (MIC). As a result, prior to thedrilling and fracking steps, water is treated to restrict theintroduction of microbes into the well or reservoir. This also acts toprevent microbes from having a negative effect on the integrity of thefluids. In addition, before disposal, flow-back water is treated toabide environmental restrictions stipulated by regulatory agencies.

Accordingly, it is an objective of the invention to replace conventionaloxidizing biocides for water treatments, such as typical equilibriumperacetic acid, hypochlorite or hypochlorous acid, and/or chlorinedioxide compositions.

It is a further objective of the invention to develop methods for watertreatment in oil and gas recovery that provide effective antimicrobialefficacy without any deleterious interaction with functional agents,including for example friction reducers and viscosity enhancers.

A further objective of the invention is to develop compositions andmethods for use of atypical peracids via distillation, perhydrolysis ofacetyl donors, and preferably use of peroxide-reducing agents, such as ametal or strong oxidizer, to improve the stability of peracids andperacid compositions and in most cases the antimicrobial efficacy of theperacid compared to the use of conventional equilibrium peracids alone.

A further objective of the invention is to develop methods usingperacids for the treatment of water used in drilling and/or fracking, aswell as treatment of water that is planned for disposal to result incleaner water with low numbers of microorganisms.

A still further objective of the invention are compositions and methodsfor using peracids, namely peracetic acid, with a peroxide-reducingagent, such as a metal or strong oxidizer, to reduce H₂O₂ in order tominimize the negative effects of H₂O₂.

Other objects, advantages and features of the present invention willbecome apparent from the following specification taken in conjunctionwith the accompanying drawings.

BRIEF SUMMARY OF THE INVENTION

In an aspect, the present invention provides a method of treating waterscomprising: (a) treating a percarboxylic acid composition with aperoxide-reducing agent to generate an antimicrobial composition; (b)providing the antimicrobial composition to a water source in need oftreatment to form a treated water source, wherein the treated watersource comprises (i) from up to about 1000 ppm inorganicperoxide-reducing agent, (ii) from about 0 wt-% to about 1 wt-% hydrogenperoxide; (iii) from about 0.0001 wt-% to about 10.0 wt-% of a C1-C22carboxylic acid; and (iv) from about 0.0001 wt-% to about 10.0 wt-% of aC1-C22 percarboxylic acid, wherein the hydrogen peroxide to peracidratio is from about 0:100 to about 1:10 by wt; and (c) directing thetreated water source into a subterranean environment or disposing of thetreated water source having a minimized environmental impact.

In a further aspect, the present invention provides a method of treatinga water source comprising: adding a percarboxylic acid andperoxide-reducing agent to the water source to form a treated watersource having a hydrogen peroxide to peracid ratio from about 0:100 toabout 1:10 by weight, wherein said antimicrobial composition in a usesolution with said treated water source comprises (i) less than about1000 ppm of an inorganic peroxide-reducing agent, (ii) from about 0 wt-%to about 1 wt-% hydrogen peroxide; (iii) from about 0.0001 wt-% to about10.0 wt-% of a C₁-C₂₂ carboxylic acid; and (iv) from about 0.0001 wt-%to about 10.0 wt-% of a C₁-C₂₂ percarboxylic acid. In a further aspect,the treated water source reduces corrosion caused by hydrogen peroxideand reduces microbial-induced corrosion, and wherein the antimicrobialcomposition does not interfere with friction reducers, viscosityenhancers, other functional ingredients found in the water source orcombinations thereof.

Surprisingly, it has been found that peroxide-reducing agents, such as ametal or strong oxidizer, are particularly effective at decomposinghydrogen peroxide in peracid compositions and in particular in peracidcompositions that are used in water treatments for oil and gas recovery.Methods and compositions for using decreased amounts/ratio of hydrogenperoxide (to peracid) provide unexpected benefits in the stability (andas an apparent result, further unexpected benefits in the efficacy) ofthe oxidizing biocides. In turn the reduced available oxygen within theperacid composition does not negatively interact with functional agents,including for example friction reducers, and provides a number ofadditional benefits for use in industrial applications and/or variousaseptic treatment applications.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1-2 show an embodiment of the invention where use of peracid withcatalase decreases the corrosion rates of carbon steel.

FIG. 3 shows the average log reduction generated after a 2.5 minute and5 minute exposure time to varying concentrations of POAA required toachieve 20 ppm residual POAA within various fracking water mixtures.

FIG. 4 shows the biocide efficiency of PAA/H₂O₂ and PAA/H₂O₂/Catalasecompositions after a 10 minute contact period according to an embodimentof the invention.

FIG. 5 shows the biocide efficiency of PAA/H₂O₂ and PAA/H₂O₂/Catalasecompositions after a 60 minute contact period according to an embodimentof the invention.

FIG. 6 shows the average log reduction generated after a 2.5 minuteexposure time to varying concentrations of POAA to achieve 20 ppmresidual POAA within fracking water mixtures.

FIG. 7 shows the average log reduction generated after a 2.5 minuteexposure time to 30 ppm or 40 ppm POAA EnviroSan with or withoutcatalase in different fracking water mixtures according to embodimentsof the invention.

FIG. 8 shows titration data of POAA in catalase treated (and untreated)solutions of the EnviroSan test substance according to embodiments ofthe invention.

FIG. 9 shows the average log reduction generated after a 2.5 minuteexposure time to 30 ppm POAA EnviroSan with or without catalasepretreatment in different fracking water mixtures according to theinvention.

FIG. 10 shows the average log reduction generated after a 5 minuteexposure time to 30 ppm POAA EnviroSan with or without catalasepretreatment in different fracking water mixtures according to theinvention.

FIG. 11 shows the average log reduction generated after a 5 minuteexposure time to 30 ppm POAA EnviroSan with or without catalase indifferent fracking water mixtures that were pretreated with 500 ppmEnviroSan product more than 1 hour before micro testing.

FIG. 12 shows the log survivors present 2.5, 5 and 60 minutes after theaddition of a P. aeruginosa culture into different mixtures of frackingwater according to embodiments of the invention.

FIG. 13 shows the average log reduction generated after a 2.5 and 5minute exposure times to 30 ppm PAA with catalase against increasinglevels of PAA alone in various fracking water mixtures.

FIG. 14 shows the impact of POAA to H₂O₂ ratio on the stability of POAAaccording to embodiments of the invention.

FIGS. 15-16 show the impact of catalase addition on the peracidstability within treatment waters according to the invention.

FIG. 17 shows the synergy of mixed peracid antimicrobial efficacy withblends of water sources according to embodiments of the invention.

FIG. 18 shows the compatibility of peracid and catalase compositions foruse in gel formation for gel frac fluids according to embodiments of theinvention.

FIG. 19 shows the compatibility of peracid and catalase compositions asa result of processes of combining the same to produce reduced peroxideperacid compositions according to embodiments of the invention.

FIG. 20 shows the impact on peracid composition stability in variouspretreated contaminated water sources according to embodiments of theinvention.

FIG. 21 shows differences in POAA composition stability according toembodiments of the invention.

FIG. 22 shows the difference in POAA decomposition within a peracidcomposition treated with an inorganic metal peroxide-reducing agent,wherein the peracid compositions have varying concentrations of hydrogenperoxide.

FIG. 23 shows the loss rate of POAA concentration in the presence of aplatinum peroxide-reducing agent.

FIG. 24 shows the decomposition of POAA compositions treated with aplatinum peroxide-reducing agent (with/without a catalaseperoxide-reducing enzyme agent) according to embodiments of theinvention.

FIG. 25 shows the decomposition of POAA and hydrogen peroxide in peracidcompositions treated with various metallic catalysts (e.g.peroxide-reducing agents) according to embodiments of the invention.

FIGS. 26-27 show POAA loss (FIG. 26) and hydrogen peroxide loss (FIG.27) as a function of time in the presence of a CoMo peroxide-reducingagent according to embodiments of the invention.

FIGS. 28-29 show POAA loss (FIG. 28) and hydrogen peroxide loss (FIG.29) as a function of time in the presence of a NiW peroxide-reducingagent according to embodiments of the invention.

FIGS. 30-33 show POAA loss (FIGS. 30, 32, 33) and hydrogen peroxide loss(FIGS. 31-33) as a function of time in the presence of a NiMoperoxide-reducing agent according to embodiments of the invention.

FIGS. 34-37 show POAA loss (FIGS. 34, 36, 37) and hydrogen peroxide loss(FIGS. 35-37) as a function of time in the presence of a Moperoxide-reducing agent according to embodiments of the invention.

Various embodiments of the present invention will be described in detailwith reference to the drawings, wherein like reference numeralsrepresent like parts throughout the several views. Reference to variousembodiments does not limit the scope of the invention. Figuresrepresented herein are not limitations to the various embodimentsaccording to the invention and are presented for exemplary illustrationof the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure relates to peracid compositions with low tosubstantially no hydrogen peroxide for use in water treatments. Inparticular, peroxycarboxylic acids treated with a peroxide-reducingagent, such as a metal or strong oxidizer, to reduce and/or eliminatehydrogen peroxide from the peroxycarboxylic acid are provided, as wellas methods for treating various water sources with the same for the usein oil and gas recovery.

The methods and compositions disclosed herein have many advantages overconventional, peracid compositions used for water treatment and/or otherantimicrobial treatments. For example, the peracid compositions treatedwith a peroxide-reducing agent (or other means to substantially reducehydrogen peroxide content) according to methods disclosed herein, havesignificantly lower levels of the oxidant hydrogen peroxide.Beneficially, the reduction and/or elimination of hydrogen peroxidecompared to un-treated peracid compositions provides improvedantimicrobial efficacy, eliminates deleterious interaction with frictionreducers and other functional ingredients used in water treatments,and/or reduces the environmental impact of treated waters wheneliminated. In addition, the treated peracid compositions have greatlyreduced off gassing potential and continue to prevent well and reservoirsouring as well as prevent microbiologically-influenced corrosion. Theseand other benefits of the present invention are disclosed herein.

The embodiments of this invention are not limited to particularperoxycarboxylic acid compositions (preferably treated with aperoxide-reducing agent, such as a metal or strong oxidizer to reducehydrogen peroxide) and methods for using the same, which can vary andare understood by skilled artisans. It is further to be understood thatall terminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting in any manner orscope. For example, all units, prefixes, and symbols may be denoted inits SI accepted form. Numeric ranges recited within the specificationare inclusive of the numbers defining the range and include each integerwithin the defined range.

It should be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to a composition containing “a compound” includes acomposition having two or more compounds. It should also be noted thatthe term “or” is generally employed in its sense including “and/or”unless the content clearly dictates otherwise.

So that the present invention may be more readily understood, certainterms are first defined. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which embodiments ofthe invention pertain. Many methods and materials similar, modified, orequivalent to those described herein can be used in the practice of theembodiments of the present invention without undue experimentation, thepreferred materials and methods are described herein. In describing andclaiming the embodiments of the present invention, the followingterminology will be used in accordance with the definitions set outbelow.

Throughout this disclosure, various aspects of this invention arepresented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible sub-ranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

As used herein, the term “about” refers to variation in the numericalquantity that can occur, for example, through typical measuring andliquid handling procedures used for making concentrates or use solutionsin the real world; through inadvertent error in these procedures;through differences in the manufacture, source, or purity of theingredients used to make the compositions or carry out the methods; andthe like. The term “about” also encompasses amounts that differ due todifferent equilibrium conditions for a composition resulting from aparticular initial mixture. Whether or not modified by the term “about”,the claims include equivalents to the quantities.

The term “cleaning,” as used herein, means to perform or aid in soilremoval, bleaching, microbial population reduction, or combinationthereof. For the purpose of this patent application, successfulmicrobial reduction is achieved when the microbial populations arereduced by at least about 50%, or by significantly more than is achievedby a wash with water. Larger reductions in microbial population providegreater levels of protection.

As used herein, “consisting essentially of” means that the methods andcompositions may include additional steps, components, ingredients orthe like, but only if the additional steps, components and/oringredients do not materially alter the basic and novel characteristicsof the claimed methods and compositions. It is understood that aspectsand embodiments of the invention described herein include “consisting”and/or “consisting essentially of” aspects and embodiments.

As used herein, the term “disinfectant” refers to an agent that killsall vegetative cells including most recognized pathogenicmicroorganisms, using the procedure described in A.O.A.C. Use DilutionMethods, Official Methods of Analysis of the Association of OfficialAnalytical Chemists, paragraph 955.14 and applicable sections, 15thEdition, 1990 (EPA Guideline 91-2). As used herein, the term “high leveldisinfection” or “high level disinfectant” refers to a compound orcomposition that kills substantially all organisms, except high levelsof bacterial spores, and is effected with a chemical germicide clearedfor marketing as a sterilant by the Food and Drug Administration. Asused herein, the term “intermediate-level disinfection” or “intermediatelevel disinfectant” refers to a compound or composition that killsmycobacteria, most viruses, and bacteria with a chemical germicideregistered as a tuberculocide by the Environmental Protection Agency(EPA). As used herein, the term “low-level disinfection” or “low leveldisinfectant” refers to a compound or composition that kills someviruses and bacteria with a chemical germicide registered as a hospitaldisinfectant by the EPA.

As used herein, the term “free,” “no,” “substantially no” or“substantially free” refers to a composition, mixture, or ingredientthat does not contain a particular compound or to which a particularcompound or a particular compound-containing compound has not beenadded. According to the invention, the reduction and/or elimination ofhydrogen peroxide according to embodiments provide hydrogenperoxide-free or substantially-free compositions. Should the particularcompound be present through contamination and/or use in a minimal amountof a composition, mixture, or ingredients, the amount of the compoundshall be less than about 3 wt-%. More preferably, the amount of thecompound is less than 2 wt-%, less than 1 wt-%, and most preferably theamount of the compound is less than 0.5 wt-%.

As used herein, the term “microorganism” refers to any noncellular orunicellular (including colonial) organism. Microorganisms include allprokaryotes. Microorganisms include bacteria (including cyanobacteria),spores, lichens, fungi, protozoa, virinos, viroids, viruses, phages, andsome algae. As used herein, the term “microbe” is synonymous withmicroorganism.

As used herein, the terms “mixed” or “mixture” when used relating to“percarboxylic acid composition,” “percarboxylic acids,”“peroxycarboxylic acid composition” or “peroxycarboxylic acids” refer toa composition or mixture including more than one percarboxylic acid orperoxycarboxylic acid.

As used herein, the term “sanitizer” refers to an agent that reduces thenumber of bacterial contaminants to safe levels as judged by publichealth requirements. In an embodiment, sanitizers for use in thisinvention will provide at least a 99.999% reduction (5-log orderreduction). These reductions can be evaluated using a procedure set outin Germicidal and Detergent Sanitizing Action of Disinfectants, OfficialMethods of Analysis of the Association of Official Analytical Chemists,paragraph 960.09 and applicable sections, 15th Edition, 1990 (EPAGuideline 91-2). According to this reference a sanitizer should providea 99.999% reduction (5-log order reduction) within 30 seconds at roomtemperature, 25±2° C., against several test organisms.

Differentiation of antimicrobial “-cidal” or “-static” activity, thedefinitions which describe the degree of efficacy, and the officiallaboratory protocols for measuring this efficacy are considerations forunderstanding the relevance of antimicrobial agents and compositions.Antimicrobial compositions can affect two kinds of microbial celldamage. The first is a lethal, irreversible action resulting in completemicrobial cell destruction or incapacitation. The second type of celldamage is reversible, such that if the organism is rendered free of theagent, it can again multiply. The former is termed microbiocidal and thelater, microbistatic. A sanitizer and a disinfectant are, by definition,agents which provide antimicrobial or microbiocidal activity. Incontrast, a preservative is generally described as an inhibitor ormicrobistatic composition

As used herein, the term “water” for treatment according to theinvention includes a variety of sources, such as freshwater, pond water,sea waters, salt water or brine source, brackish water, recycled water,or the like. Waters are also understood to optionally include both freshand recycled water sources (e.g. “produced waters”), as well as anycombination of waters for treatment according to the invention.

As used herein, “weight percent,” “wt-%,” “percent by weight,” “% byweight,” and variations thereof refer to the concentration of asubstance as the weight of that substance divided by the total weight ofthe composition and multiplied by 100. It is understood that, as usedhere, “percent,” “%,” and the like are intended to be synonymous with“weight percent,” “wt-%,” etc.

EMBODIMENTS OF THE INVENTION

The invention generally relates to the use of peroxide-reducing agents,such as a metal or strong oxidizer, for use with peracid compositions.The invention uses the peroxide-reducing agents with peracidcompositions for use in water treatments in the field of oil and gasrecovery. The invention further relates to the use of additional methodsto reduce and/or eliminate hydrogen peroxide from peracids to providesimilar benefits to a peracid composition. Additional methods whichproduce a very low hydrogen peroxide to peracid ratio are similarlyadvantageous and suitable for use according to the invention, includingthose disclosed in U.S. Provisional Patent Application Ser. No.61/710,631, filed Oct. 5, 2012, and entitled “Stable PeroxycarboxylicAcid Compositions and Uses Thereof,” and the conversion application Ser.No. 13/839,806, now issued U.S. Pat. No. 9,267,236, which are hereinincorporated by reference in their entirety. These may include, forexample, equilibrium peracid compositions distilled to recover a verylow hydrogen peroxide peracid mixture, other catalysts for hydrogenperoxide decomposition (e.g. biomimetic complexes) and/or the use ofperhydrolysis of peracid precursors, such as esters (e.g triacetin) andamides with alkyl leaving groups ranging in carbon chain lengths ofC1-C8, to obtain peracids with very low hydrogen peroxide.

Compositions

The compositions of the invention may comprise, consist of and/orconsist essentially of a peracid composition having a low hydrogenperoxide to peracid ratio. In an aspect, the peracid composition has ahydrogen peroxide to peracid ratio in a concentrated composition fromabout 0:100 to about 1:10, preferably from about 0.5:100 to about 1:100,and more preferably from about 1:100 to 1:10. The compositions of theinvention may comprise, consist of and/or consist essentially of aperacid composition and a peroxide-reducing agent used to obtain aresultant peracid composition having a low hydrogen peroxide to peracidratio. In equilibrium chemistries there is a dynamic equilibrium betweenperacids, respective carboxylic acids, hydrogen peroxide and water in acomposition. For example, a peracetic acid composition further includesacetic acid, hydrogen peroxide and water in the aqueous commercialformulation. Accordingly, the compositions of the invention may furthercomprise, consist of and/or consist essentially of a peracidcomposition, carboxylic acid, hydrogen peroxide, and a peroxide-reducingagent. In other aspects, additional functional ingredients, such as afriction reducer, corrosion inhibitor, viscosity enhancer and/oradditional antimicrobial agent are employed in the compositions. Inother aspects, no additional functional ingredients are employed in thecompositions.

Peroxide-Reducing Agents

In an aspect of the invention, a peroxide-reducing agent is used toreduce and/or eliminate the concentration of hydrogen peroxide in anantimicrobial peracid composition. In some aspects, theperoxide-reducing agent is a peroxide-reducing inorganic agent. In anaspect of the invention, the agent is a metal and/or a strong oxidizingagent. The metal catalyzes the decomposition of hydrogen peroxide towater and oxygen. Further, the metal catalyzes the decomposition of theperacid in equilibrium. Without being limited to a particular mechanismof the invention, the decomposition of the hydrogen peroxide and peracidof an equilibrium peracid composition catalyzed by the peroxide-reducingagent beneficially results in an accelerated oxidation reaction causingincreased or enhanced antimicrobial efficacy.

Beneficially, the reduction and/or elimination of hydrogen peroxide(e.g. an oxidizer) further results in other additives for a watertreatment source (e.g. water source) not being degraded or renderedincompatible. This is critical as various additives used to enhanceand/or modify the characteristics of aqueous fluids used in welldrilling, recovery and/or production applications are at risk ofdegradation by the oxidizing effects of hydrogen peroxide. These mayinclude for example, friction reducers, scale inhibitors and viscosityenhancers used in commercial well drilling, well completion andstimulation, or production applications. According to an aspect of theinvention, the significant reduction in hydrogen peroxide from a peracidcomposition reduces or eliminates these compatibility and/or degradationconcerns.

In an aspect, the peroxide-reducing agent is a metal, combination ofmetals and/or a metal compound. Examples of suitable metals for use asthe peroxide-reducing agents (e.g. decomposition agents) include heavymetals. In a further aspect, metal oxides may be employed according tothe invention. For example, suitable metals include platinum, palladium,bismuth, tin, copper, manganese, iron, tungsten, zirconium, ruthenium,cobalt, molybdenum, nickel, iron, copper and/or manganese. In apreferred aspect, the metals include platinum, tungsten, zirconium,ruthenium, cobalt, molybdenum, nickel, iron, copper and/or manganese. Ina further preferred aspect of use in field operations for well drilling,recovery and/or production applications, the metals include iron, copperand/or manganese. In further aspects of the invention, a combination ofmetals can be employed as the peroxide-reducing agent.

In an aspect, the peroxide-reducing agent is a strong oxidizer. Withoutbeing limited to a particular mechanism of action of the compositionsand/or methods of the invention, the oxidizer has greater oxidizingpotential that hydrogen peroxide, beneficially allowing thedecomposition of the oxidant hydrogen peroxide. Examples of suitablestrong oxidizers for use as peroxide-reducing agents include halideanions, halide salts and/or halide sources, including for examplebromide and/or bromine, iodide and/or iodine, chloride and/or chlorine,fluoride and/or fluorine, etc. In a particular aspect, theperoxide-reducing agent is a chlorine sources, including, for example,hypochlorite or sodium hypochlorite, chlorine dioxide, or the like.

In a further aspect of the invention, the agent is not UV-sensitive. Ina further aspect of the invention, the metals and/or strong oxidizingagents have a high ability to decompose hydrogen peroxide. In someaspects, the peroxide-reducing agents are able to degrade at least about500 ppm of hydrogen peroxide in a peracid composition in 15 minutes. Inother aspects, the metals and/or strong oxidizing agents also have ahigh ability to decompose hydrogen peroxide at low concentrations. Insome embodiments, the concentration of metals and/or strong oxidizingagents needed to degrade 500 ppm of hydrogen peroxide in a peracidcomposition in 15 minutes is less than 200 ppm, less than 100 ppm, andless than 50 ppm.

Beneficially, the reduction or elimination of hydrogen peroxide fromoxidizing compositions obviate the various detriments caused byoxidizing agents in the various field operations for well drilling,recovery and/or production applications (and others set forth accordingto the methods of the invention). In particular, the use of theperoxide-reducing agents) with the peracid compositions providesenhanced antimicrobial benefits without causing the damage associatedwith conventional oxidizing agents (e.g. peracetic acid, hypochlorite orhypochlorous acid, and/or chlorine dioxide), such as corrosion. In afurther aspect, the reduction of hydrogen peroxide also benefits thestability of gel formation in gel frac fluids. Without being limited toa mechanism of the invention, the reduction of hydrogen peroxide in aperacid composition beneficially allows a gel frac fluid to maintain thegel for a sufficient period of time (before it breaks apart within thesubterranean environment). In some aspects, the reduction of thehydrogen peroxide within a peracid composition according to theinvention provides a suitable level of peroxide from about 1 ppm toabout 50 ppm, from about 1 ppm to about 25 ppm, or preferably from about5 ppm to about 15 ppm to maintain a stable gel frac fluid for anextended period of time.

In an aspect, the peroxide-reducing agents preferentially decomposehydrogen peroxide from a peracid composition (e.g. a greater percentageof peracid concentration remains in a treated peracid composition incomparison to hydrogen peroxide). Without limiting the scope ofperoxide-reducing agents suitable for use according to the invention, inan aspect the agent preferentially reduces hydrogen peroxide over theperacid. In a further aspect, the agent reduces at least about 2:1hydrogen peroxide to peracid, or greater. In a further aspect, the agentreduces at least about 1.5:1 hydrogen peroxide to peracid, or greater.

In some embodiments, the peroxide-reducing agent is able to degrade atleast about 50% of the initial concentration of hydrogen peroxide in aperacid composition. Preferably, the agent is provided in sufficientamount to reduce the hydrogen peroxide concentration of a peracidcomposition by at least more than about 50%, more preferably at leastabout 60%, at least about 70%, at least about 80%, or at least about90%. In some embodiments, the peroxide-reducing agent reduces thehydrogen peroxide concentration of a peracid composition by more thanabout 90%. Without limiting the scope of invention, the numeric rangesare inclusive of the numbers defining the range and include each integerwithin the defined range.

In an aspect of the invention, the peroxide-reducing agents are suitablefor use and have a tolerance to a wide range of temperatures, includingthe temperatures ranges in water treatment applications which may rangefrom about 0-180° C. Although temperature and other ambient conditionsmay affect the stability of the agents, a suitable peroxide-reducingagent will maintain at least 50% of its activity under such storageand/or application temperatures for at least about 10 minutes,preferably for at least about 1 hour, and more preferably for at leastabout 24 hours. Without limiting the scope of invention, the numericranges are inclusive of the numbers defining the range and include eachinteger within the defined range.

In a further aspect of the invention, the peroxide-reducing agentsdescribed herein have a tolerance to pH ranges found in water treatmentapplications. Acetic acid levels (or other carboxylic acid) in a watertreatment application can widely range in parts per million (ppm) ofacetic or other carboxylic acid. The solutions will have a correspondingrange of pH range from greater than 0 to about 10. A suitableperoxide-reducing agent will maintain at least about 50% of its activityin such solutions of acetic or other carboxylic acid over a period ofabout 10 minutes, preferably for at least about 1 hour, and morepreferably for at least about 24 hours. Without limiting the scope ofinvention, the numeric ranges are inclusive of the numbers defining therange and include each integer within the defined range.

In an aspect of the invention, a peroxide-reducing agent is present in ause solution of the water treatment and peracid composition insufficient amounts to reduce the concentration of hydrogen peroxide fromthe peracid composition within at least a few hours, preferably withinless than 10 hours, preferably within less than 5 hours, preferablywithin less than 4 hours, and still more preferably within less than 1hour. In an aspect of the invention, a peroxide-reducing agent ispresent in a use solution of the water treatment and peracid compositionin sufficient amounts to reduce the concentration of hydrogen peroxidefrom the peracid composition by at least 50% within about 10 minutes,preferably within about 5 minutes, preferably within about 2 to 5minutes, more preferably within about 1 minute. The ranges ofconcentration of the agents will vary depending upon the amount of timewithin which 50% of the hydrogen peroxide from the peracid compositionis removed.

In certain aspects of the invention, a peroxide-reducing agent ispresent in a use solution composition including the water source to betreated in amounts of at least about 0.5 ppm, preferably between about0.5 ppm and about 1000 ppm, preferably between about 0.5 ppm and about500 ppm, preferably between about 0.5 ppm and 100 ppm, and morepreferably between about 1 ppm and about 100 ppm. Without limiting thescope of invention, the numeric ranges are inclusive of the numbersdefining the range and include each integer within the defined range.

The peroxide-reducing agents employed may be free floating in the usesolution composition, meaning that the agent is part of the composition,without being bound to a surface.

Alternatively, the peroxide-reducing agents may be immobilized on asurface that is in fluid communication with the use solution compositionin way that allows the agent to interact with and decompose hydrogenperoxide from the peracid compositions. In some aspects, immobilizedagents may be more stable than unbound, soluble agents. In some aspects,immobilized agents may also have increased thermal and pH stabilitywhich might be due to the protection of the substrate provides againstsudden thermal and pH changes. An immobilized agent also has theadvantage of being able to be removed from the rest of the compositioneasily. An immobilized agent may include an agent attached to asubstrate. Examples of substrates may include for example zeolites,polyurethane foams, polyacrylamide gels, polyethylene maleic anhydridegels, polystyrene maleic anhydride gels, cellulose, nitrocellulose,silastic resins, porous glass, macroporous glass membranes, glass beads,activated clay, zeolites, alumina, silica, silicate and other inorganicand organic substrates. The peroxide-reducing agent may be attached tothe substrate in various ways including carrier covalent binding,crosslinking, physical adsorption, ionic binding, and entrapping.

In an aspect, the peroxide-reducing agent is added into a peracid usesolution instead of a concentrated peracid composition. Without beinglimited to a mechanism of action, the use of a peroxide-reducing agentis preferably added to a non-concentrated peracid composition in orderto maintain the viability and peroxide-reducing capability of the agent.For example, in an aspect, a concentrated peracid composition (e.g.about 10 wt-% or greater peracid, or about 15 wt-% or greater peracid)is diluted into a water source and thereafter the peroxide-reducingagent is added. In an aspect, the dilute water source may be the watersource in need of treatment according to the invention. In anotheraspect, the dilute water source may be a use solution of the peracidcomposition (or less concentrated peracid composition) for subsequentdosing into the water source in need of treatment according to theinvention.

Peroxide-Reducing Enzymes

In some aspects, the peroxide-reducing agent is a peroxide-reducingenzyme. In an aspect of the invention, a catalase or peroxidase enzymeis used to reduce and/or eliminate the concentration of hydrogenperoxide in an antimicrobial peracid composition. The enzymes catalyzethe decomposition of hydrogen peroxide to water and oxygen.Beneficially, the reduction and/or elimination of hydrogen peroxide(strong oxidizer) results in other additives for a water treatmentsource (e.g. water source) not being degraded or rendered incompatible.Various additives used to enhance or modify the characteristics of theaqueous fluids used in well drilling, recovery and productionapplications are at risk of degradation by the oxidizing effects ofhydrogen peroxide. These may include for example, friction reducers,scale inhibitors and viscosity enhancers used in commercial welldrilling, well completion and stimulation, or production applications.

Various sources of catalase enzymes (or other peroxide-reducing enzymeagents) may be employed according to the invention, including: animalsources such as bovine catalase isolated from beef livers; fungalcatalases isolated from fungi including Penicillium chrysogenum,Penicillium notatum, and Aspergillus niger; plant sources; bacterialsources such as Staphylcoccus aureus, and genetic variations andmodifications thereof. In an aspect of the invention, fungal catalasesare utilized to reduce the hydrogen peroxide content of a peracidcomposition.

Catalases (or other peroxide-reducing enzyme agents) are commerciallyavailable in various forms, including liquid and spray dried forms.Commercially available catalase includes both the active enzyme as wellas additional ingredients to enhance the stability of the enzyme. Someexemplary commercially available catalase enzymes include GenencorCA-100 and CA-400, as well as Mitsubishi Gas and Chemical (MGC) ASCsuper G and ASC super 200. Additional description of suitable catalaseenzymes are disclosed and herein incorporated by reference in itsentirety from U.S. Patent Publication No. 2012/0321510 and U.S. Pat.Nos. 8,241,624, 8,231,917 and 8,226,939, which are herein incorporatedby reference in their entirety.

In an aspect of the invention, catalase enzymes (or otherperoxide-reducing enzyme agents) have a high ability to decomposehydrogen peroxide. In some aspects, catalase enzymes (or otherperoxide-reducing enzyme agents) used in this invention include enzymeswith a high ability to decompose hydrogen peroxide. In some embodiments,the enzyme is able to degrade at least about 500 ppm of hydrogenperoxide in a peracid composition in 15 minutes. In other aspects,enzymes used in this invention include catalase enzymes (or otherperoxide-reducing enzyme agents) with a high ability to decomposehydrogen peroxide at low concentrations. In some embodiments, theconcentration of enzyme needed to degrade 500 ppm of hydrogen peroxidein a peracid composition in 15 minutes is less than 200 ppm, less than100 ppm, and less than 50 ppm.

Beneficially, the reduction or elimination of hydrogen peroxide fromoxidizing compositions obviates the various detriments caused byoxidizing agents. In particular, the use of catalase (or otherperoxide-reducing enzyme agents) with the peracids compositions providesenhanced antimicrobial benefits without causing the damage associatedwith conventional oxidizing agents (e.g. peracetic acid, hypochlorite orhypochlorous acid, and/or chlorine dioxide), such as corrosion.

Peroxidase enzymes (or other peroxide-reducing enzyme agents) may alsobe employed to decompose hydrogen peroxide from a peracid composition.Although peroxidase enzymes primarily function to enable oxidation ofsubstrates by hydrogen peroxide, they are also suitable for effectivelylowering hydrogen peroxide to peracid ratios in compositions. Varioussources of peroxidase enzymes (or other peroxide-reducing enzyme agents)may be employed according to the invention, including for example animalsources, fungal peroxidases, and genetic variations and modificationsthereof. Peroxidases are commercially available in various forms,including liquid and spray dried forms. Commercially availableperoxidases include both the active enzyme as well as additionalingredients to enhance the stability of the enzyme.

In some embodiments, the peroxide-reducing enzyme is able to degrade atleast about 50% of the initial concentration of hydrogen peroxide in aperacid composition. Preferably, the enzyme is provided in sufficientamount to reduce the hydrogen peroxide concentration of a peracidcomposition by at least more than about 50%, more preferably at leastabout 60%, at least about 70%, at least about 80%, at least about 90%.In some embodiments, the enzyme reduces the hydrogen peroxideconcentration of a peracid composition by more than 90%. Withoutlimiting the scope of invention, the numeric ranges are inclusive of thenumbers defining the range and include each integer within the definedrange.

In an aspect of the invention, the peroxide-reducing enzymes aresuitable for use and have a tolerance to a wide range of temperatures,including the temperatures ranges in water treatment applications whichmay range from about 0-180° C. Although temperature and other ambientconditions may affect the stability of the enzymes, a suitableperoxide-reducing enzyme will maintain at least 50% of its activityunder such storage and/or application temperatures for at least about 10minutes, preferably for at least about 1 hour, and more preferably forat least about 24 hours. Without limiting the scope of invention, thenumeric ranges are inclusive of the numbers defining the range andinclude each integer within the defined range.

In a further aspect of the invention, the peroxide-reducing enzymesdescribed herein have a tolerance to pH ranges found in water treatmentapplications. Acetic acid levels (or other carboxylic acid) in a watertreatment application can widely range in parts per million (ppm) ofacetic or other carboxylic acid. The solutions will have a correspondingrange of pH range from greater than 0 to about 10. A suitableperoxide-reducing enzyme will maintain at least about 50% of itsactivity in such solutions of acetic or other carboxylic acid over aperiod of about 10 minutes, preferably for at least about 1 hour, andmore preferably for at least about 24 hours. Without limiting the scopeof invention, the numeric ranges are inclusive of the numbers definingthe range and include each integer within the defined range.

In an aspect of the invention, a peroxide-reducing enzyme is present ina use solution of the water treatment and peracid composition insufficient amounts to reduce the concentration of hydrogen peroxide fromthe peracid composition to sufficiently reduced or eliminatedconcentration within at least a few hours, preferably within less than10 hours, preferably within less than 5 hours, preferably within lessthan 4 hours, and still more preferably within less than 1 hour. In anaspect of the invention, a peroxide-reducing enzyme is present in a usesolution of the water treatment and peracid composition in sufficientamounts to reduce the concentration of hydrogen peroxide from theperacid composition by at least 50% within about 10 minutes, preferablywithin about 5 minutes, preferably within about 2 to 5 minutes, morepreferably within about 1 minute. The ranges of concentration of theenzymes will vary depending upon the amount of time within which 50% ofthe hydrogen peroxide from the peracid composition is removed.

In certain aspects of the invention, a peroxide-reducing enzyme ispresent in a use solution composition including the water source to betreated in amounts of at least about 0.5 ppm, preferably between about0.5 ppm and about 1000 ppm, preferably between about 0.5 ppm and about500 ppm, preferably between about 0.5 ppm and 100 ppm, and morepreferably between about 1 ppm and about 100 ppm. Without limiting thescope of invention, the numeric ranges are inclusive of the numbersdefining the range and include each integer within the defined range.

The enzymes employed may be free floating in the use solutioncomposition, meaning that the enzyme is part of the composition, withoutbeing bound to a surface.

Alternatively, the enzymes may be immobilized on a surface that is influid communication with the use solution composition in way that allowsthe enzyme to interact with and decompose hydrogen peroxide from theperacid compositions. Immobilized enzyme may be more stable thanunbound, soluble enzyme. Immobilized enzyme also shows increased thermaland pH stability which might be due to the protection of the substrateprovides against sudden thermal and pH changes. An immobilized enzymealso has the advantage of being able to be removed from the rest of thecomposition easily. An immobilized enzyme may include a soluble enzymethat is attached to a substrate. Examples of substrates may includepolyurethane foams, polyacrylamide gels, polyethylene maleic anhydridegels, polystyrene maleic anhydride gels, cellulose, nitrocellulose,silastic resins, porous glass, macroporous glass membranes, glass beads,activated clay, zeolites, alumina, silica, silicate and other inorganicand organic substrates. The enzyme may be attached to the substrate invarious ways including carrier covalent binding, crosslinking, physicaladsorption, ionic binding, and entrapping.

In an aspect, the peroxide-reducing enzyme is added into a peracid usesolution instead of a concentrated peracid composition. Without beinglimited to a mechanism of action, the use of a peroxide-reducing enzymeagent is preferably added to a non-concentrated peracid composition inorder to maintain the viability and peroxide-reducing capability of theagent. For example, in an aspect, a concentrated peracid composition(e.g. about 10 wt-% or greater peracid, or about 15 wt-% or greaterperacid) is diluted into a water source and thereafter theperoxide-reducing enzyme agent is added. In an aspect, the dilute watersource may be the water source in need of treatment according to theinvention. In another aspect, the dilute water source may be a usesolution of the peracid composition (or less concentrated peracidcomposition) for subsequent dosing into the water source in need oftreatment according to the invention.

Peracids

In some aspects, a peracid is included for antimicrobial efficacy in thecompositions for water treatment. As used herein, the term “peracid” mayalso be referred to as a “percarboxylic acid” or “peroxyacid.”Sulfoperoxycarboxylic acids, sulfonated peracids and sulfonatedperoxycarboxylic acids are also included within the term “peracid” asused herein. The terms “sulfoperoxycarboxylic acid,” “sulfonatedperacid,” or “sulfonated peroxycarboxylic acid” refers to theperoxycarboxylic acid form of a sulfonated carboxylic acid as disclosedin U.S. Pat. No. 8,344,026, and U.S. Patent Publication Nos.2010/0048730 and 2012/0052134, each of which are incorporated herein byreference in their entirety. As one of skill in the art appreciates, aperacid refers to an acid having the hydrogen of the hydroxyl group incarboxylic acid replaced by a hydroxy group. Oxidizing peracids may alsobe referred to herein as peroxycarboxylic acids.

A peracid includes any compound of the formula R—(COOOH)_(n) in which Rcan be hydrogen, alkyl, alkenyl, alkyne, acrylic, alicyclic group, aryl,heteroaryl, or heterocyclic group, and n is 1, 2, or 3, and named byprefixing the parent acid with peroxy. Preferably R includes hydrogen,alkyl, or alkenyl. The terms “alkyl,” “alkenyl,” “alkyne,” “acrylic,”“alicyclic group,” “aryl,” “heteroaryl,” and “heterocyclic group” are asdefined herein.

As used herein, the term “alkyl” includes a straight or branchedsaturated aliphatic hydrocarbon chain having from 1 to 22 carbon atoms,such as, for example, methyl, ethyl, propyl, isopropyl (1-methylethyl),butyl, tert-butyl (1,1-dimethylethyl), and the like. The term “alkyl” or“alkyl groups” also refers to saturated hydrocarbons having one or morecarbon atoms, including straight-chain alkyl groups (e.g., methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.),cyclic alkyl groups (or “cycloalkyl” or “alicyclic” or “carbocyclic”groups) (e.g., cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, etc.), branched-chain alkyl groups (e.g., isopropyl,tert-butyl, sec-butyl, isobutyl, etc.), and alkyl-substituted alkylgroups (e.g., alkyl-substituted cycloalkyl groups andcycloalkyl-substituted alkyl groups).

Unless otherwise specified, the term “alkyl” includes both“unsubstituted alkyls” and “substituted alkyls.” As used herein, theterm “substituted alkyls” refers to alkyl groups having substituentsreplacing one or more hydrogens on one or more carbons of thehydrocarbon backbone. Such substituents may include, for example,alkenyl, alkynyl, halogeno, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate,alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl,alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl,phosphate, phosphonato, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino),acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyland ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonates, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic(including heteroaromatic) groups.

The term “alkenyl” includes an unsaturated aliphatic hydrocarbon chainhaving from 2 to 12 carbon atoms, such as, for example, ethenyl,1-propenyl, 2-propenyl, 1-butenyl, 2-methyl-1-propenyl, and the like.The alkyl or alkenyl can be terminally substituted with a heteroatom,such as, for example, a nitrogen, sulfur, or oxygen atom, forming anaminoalkyl, oxyalkyl, or thioalkyl, for example, aminomethyl, thioethyl,oxypropyl, and the like. Similarly, the above alkyl or alkenyl can beinterrupted in the chain by a heteroatom forming an alkylaminoalkyl,alkylthioalkyl, or alkoxyalkyl, for example, methylaminoethyl,ethylthiopropyl, methoxymethyl, and the like.

Further, as used herein the term “alicyclic” includes any cyclichydrocarbyl containing from 3 to 8 carbon atoms. Examples of suitablealicyclic groups include cyclopropanyl, cyclobutanyl, cyclopentanyl,etc. The term “heterocyclic” includes any closed ring structuresanalogous to carbocyclic groups in which one or more of the carbon atomsin the ring is an element other than carbon (heteroatom), for example, anitrogen, sulfur, or oxygen atom. Heterocyclic groups may be saturatedor unsaturated. Examples of suitable heterocyclic groups include forexample, aziridine, ethylene oxide (epoxides, oxiranes), thiirane(episulfides), dioxirane, azetidine, oxetane, thietane, dioxetane,dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane,dihydrofuran, and furan. Additional examples of suitable heterocyclicgroups include groups derived from tetrahydrofurans, furans, thiophenes,pyrrolidines, piperidines, pyridines, pyrrols, picoline, coumaline, etc.

According to the invention, alkyl, alkenyl, alicyclic groups, andheterocyclic groups can be unsubstituted or substituted by, for example,aryl, heteroaryl, C₁₋₄ alkyl, C₁₋₄ alkenyl, C₁₋₄ alkoxy, amino, carboxy,halo, nitro, cyano, —SO₃H, phosphono, or hydroxy. When alkyl, alkenyl,alicyclic group, or heterocyclic group is substituted, preferably thesubstitution is C₁₋₄ alkyl, halo, nitro, amido, hydroxy, carboxy,sulpho, or phosphono. In one embodiment, R includes alkyl substitutedwith hydroxy. The term “aryl” includes aromatic hydrocarbyl, includingfused aromatic rings, such as, for example, phenyl and naphthyl. Theterm “heteroaryl” includes heterocyclic aromatic derivatives having atleast one heteroatom such as, for example, nitrogen, oxygen, phosphorus,or sulfur, and includes, for example, furyl, pyrrolyl, thienyl,oxazolyl, pyridyl, imidazolyl, thiazolyl, isoxazolyl, pyrazolyl,isothiazolyl, etc. The term “heteroaryl” also includes fused rings inwhich at least one ring is aromatic, such as, for example, indolyl,purinyl, benzofuryl, etc.

According to the invention, aryl and heteroaryl groups can beunsubstituted or substituted on the ring by, for example, aryl,heteroaryl, alkyl, alkenyl, alkoxy, amino, carboxy, halo, nitro, cyano,—SO₃H, phosphono, or hydroxy. When aryl, aralkyl, or heteroaryl issubstituted, preferably the substitution is C₁₋₄ alkyl, halo, nitro,amido, hydroxy, carboxy, sulpho, or phosphono. In one embodiment, Rincludes aryl substituted with C₁₋₄ alkyl.

Peracids suitable for use include any peroxycarboxylic acids, includingvarying lengths of peroxycarboxylic and percarboxylic acids (e.g. C1-22)that can be prepared from the acid-catalyzed equilibrium reactionbetween a carboxylic acid described above and hydrogen peroxide. Aperoxycarboxylic acid can also be prepared by the auto-oxidation ofaldehydes or by the reaction of hydrogen peroxide with an acid chloride,acid hydride, carboxylic acid anhydride, or sodium alcoholate.Alternatively, peracids can be prepared through non-equilibriumreactions, which may be generated for use in situ, such as the methodsdisclosed in U.S. Patent Publication Nos. 2012/0172440 and 2012/0172441each titled “In Situ Generation of Peroxycarboxylic Acids at AlkalinepH, and Methods of Use Thereof,” which are incorporated herein byreference in their entirety. Preferably a composition of the inventionincludes peroxyacetic acid, peroxyoctanoic acid, peroxypropionic acid,peroxylactic acid, peroxyheptanoic acid, peroxyoctanoic acid and/orperoxynonanoic acid.

In some embodiments, a peroxycarboxylic acid includes at least onewater-soluble peroxycarboxylic acid in which R includes alkyl of 1-22carbon atoms. For example, in one embodiment, a peroxycarboxylic acidincludes peroxyacetic acid. In another embodiment, a peroxycarboxylicacid has R that is an alkyl of 1-22 carbon atoms substituted withhydroxy. Methods of preparing peroxyacetic acid are known to those ofskill in the art including those disclosed in U.S. Pat. No. 2,833,813,which is herein incorporated herein by reference in its entirety.

In another embodiment, a sulfoperoxycarboxylic acid has the followingformula:

wherein R₁ is hydrogen, or a substituted or unsubstituted alkyl group;R₂ is a substituted or unsubstituted alkylene group; X is hydrogen, acationic group, or an ester forming moiety; or salts or esters thereof.In some embodiments, R₁ is a substituted or unsubstituted C_(m) alkylgroup; X is hydrogen a cationic group, or an ester forming moiety; R₂ isa substituted or unsubstituted C_(n) alkyl group; m=1 to 10; n=1 to 10;and m+n is less than 18, or salts, esters or mixtures thereof.

In some embodiments, R₁ is hydrogen. In other embodiments, R₁ is asubstituted or unsubstituted alkyl group. In some embodiments, R₁ is asubstituted or unsubstituted alkyl group that does not include a cyclicalkyl group. In some embodiments, R₁ is a substituted alkyl group. Insome embodiments, R₁ is an unsubstituted C₁-C₉ alkyl group. In someembodiments, R₁ is an unsubstituted C₇ or C₈ alkyl. In otherembodiments, R₁ is a substituted C₈-C₁₀alkylene group. In someembodiments, R₁ is a substituted C₈-C₁₀ alkyl group is substituted withat least 1, or at least 2 hydroxyl groups. In still yet otherembodiments, R₁ is a substituted C₁-C₉ alkyl group. In some embodiments,R₁ is a substituted C₁-C₉ substituted alkyl group is substituted with atleast 1 SO₃H group. In other embodiments, R₁ is a C₉-C₁₀ substitutedalkyl group. In some embodiments, R₁ is a substituted C₉-C₁₀alkyl groupwherein at least two of the carbons on the carbon backbone form aheterocyclic group. In some embodiments, the heterocyclic group is anepoxide group.

In some embodiments, R₂ is a substituted C₁-C₁₀alkylene group. In someembodiments, R₂ is a substituted C₈-C₁₀alkylene. In some embodiments, R₂is an unsubstituted C₆-C₉ alkylene. In other embodiments, R₂ is aC₈-C₁₀alkylene group substituted with at least one hydroxyl group. Insome embodiments, R₂ is a C₁₀ alkylene group substituted with at leasttwo hydroxyl groups. In other embodiments, R₂ is a C₈ alkylene groupsubstituted with at least one SO₃H group. In some embodiments, R₂ is asubstituted C₉ group, wherein at least two of the carbons on the carbonbackbone form a heterocyclic group. In some embodiments, theheterocyclic group is an epoxide group. In some embodiments, R₁ is aC₈-C₉ substituted or unsubstituted alkyl, and R₂ is a C₇-C₈ substitutedor unsubstituted alkylene.

These and other suitable sulfoperoxycarboxylic acid compounds for use inthe stabilized peroxycarboxylic acid compositions of the invention arefurther disclosed in U.S. Pat. No. 8,344,026 and U.S. Patent PublicationNos. 2010/0048730 and 2012/0052134, which are incorporated herein byreference in its entirety.

In additional embodiments a sulfoperoxycarboxylic acid is combined witha single or mixed peroxycarboxylic acid composition, such as asulfoperoxycarboxylic acid with peroxyacetic acid, peroxyoctanoic acidand sulfuric acid (PSOA/POOA/POAA/H₂SO₄). In other embodiments, a mixedperacid is employed, such as a peroxycarboxylic acid including at leastone peroxycarboxylic acid of limited water solubility in which Rincludes alkyl of 5-22 carbon atoms and at least one water-solubleperoxycarboxylic acid in which R includes alkyl of 1-4 carbon atoms. Forexample, in one embodiment, a peroxycarboxylic acid includesperoxyacetic acid and at least one other peroxycarboxylic acid such asthose named above. Preferably a composition of the invention includesperoxyacetic acid and peroxyoctanoic acid. Other combinations of mixedperacids are well suited for use in the current invention.

In another embodiment, a mixture of peracetic acid and peroctanoic acidis used to treat a water source, such as disclosed in U.S. Pat. No.5,314,687 which is herein incorporated by reference in its entirety. Inan aspect, the peracid mixture is a hydrophilic peracetic acid and ahydrophobic peroctanoic acid, providing antimicrobial synergy. In anaspect, the synergy of a mixed peracid system allows the use of lowerdosages of the peracids.

In another embodiment, a tertiary peracid mixture composition, such asperoxysulfonated oleic acid, peracetic acid and peroctanoic acid areused to treat a water source, such as disclosed in U.S. Pat. No.8,344,026 which is incorporated herein by reference in its entirety. Acombination of the three peracids provides significant antimicrobialsynergy providing an efficient antimicrobial composition for the watertreatment methods according to the invention. In addition, it is thoughtthe high acidity built in the composition assists in removing chemicalcontaminants from the water (e.g. sulfite and sulfide species), and thedefoaming agent (e.g. aluminum sulfate) provides defoaming (e.g.combating foam caused by any anionic surface active agents used in thewater treatment).

Advantageously, a combination of peroxycarboxylic acids provides acomposition with desirable antimicrobial activity in the presence ofhigh organic soil loads. The mixed peroxycarboxylic acid compositionsoften provide synergistic micro efficacy. Accordingly, compositions ofthe invention can include a peroxycarboxylic acid, or mixtures thereof.

Various commercial formulations of peracids are available, including forexample peracetic acid (15%) and hydrogen peroxide (10%) available asEnviroSan (Ecolab, Inc., St. Paul Minn.). Most commercial peracidsolutions state a specific percarboxylic acid concentration withoutreference to the other chemical components in a use solution. However,it should be understood that commercial products, such as peraceticacid, will also contain the corresponding carboxylic acid (e.g. aceticacid), hydrogen peroxide and water.

In an aspect, any suitable C₁-C₂₂ percarboxylic acid can be used in thepresent compositions. In some embodiments, the C₁-C₂₂ percarboxylic acidis a C₂-C₂₀ percarboxylic acid. In other embodiments, the C₁-C₂₂percarboxylic is a C₁, C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂,C₁₃, C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, C₁₉, C₂₀, C₂₁, or C₂₂ carboxylic acid. Instill other embodiments, the C₁-C₂₂ percarboxylic acid comprisesperoxyacetic acid, peroxyoctanoic acid and/or peroxysulfonated oleicacid.

In an aspect of the invention, a peracid is present in a use solutionwith the water source in need of treatment in an amount of between about1 ppm and about 5000 ppm, preferably between about 1 ppm and about 2000ppm, preferably between about 1 ppm and about 1000 ppm, and morepreferably between about 1 ppm and about 100 ppm. Without limiting thescope of invention, the numeric ranges are inclusive of the numbersdefining the range and include each integer within the defined range.The amount of peracid above the preferred range of 100 ppm may beemployed for highly contaminated waters in need of treatment, such assource waters including increased amounts of produced water (e.g.recycled waters).

In an aspect of the invention, a peracid may be selected from aconcentrated composition having a ratio of hydrogen peroxide to peracidfrom about 0:100 to about 0.5:100, preferably from about 0.5:100 toabout 1:10. Various concentrated peracid compositions having thehydrogen peroxide to peracid ratios of about 0:100 to about 0.5:100,preferably from about 0.5:100 to about 1:10 may be employed to produce ause solution for treatment according to the methods of the invention. Ina further aspect of the invention, a peracid may have a ratio ofhydrogen peroxide to peracid as low as from about 0.001 part or 0.01part hydrogen peroxide to about 1 part peracid. Preferably, any ratiowherein the amount of hydrogen peroxide is less than peracid is suitablefor use according to the invention in formulating a use solution forwater treatments. Without limiting the scope of invention, the numericranges are inclusive of the numbers defining the range and include eachinteger within the defined range.

Obtaining the preferred hydrogen peroxide to peroxycarboxylic acidratios in a peracid composition may be obtained by a variety of methodssuitable for producing a very low hydrogen peroxide to peracid ratio. Inan aspect, equilibrium peracid compositions may be distilled to recovera very low hydrogen peroxide peracid mixture. In yet another aspect,catalysts for hydrogen peroxide decomposition may be combined with aperacid composition, including for example, peroxide-reducing agentsand/or other biomimetic complexes. In yet another aspect, perhydrolysisof peracid precursors, such as esters (e.g. triacetin) and amides may beemployed to obtain peracids with very low hydrogen peroxide.

In a particularly preferred aspect, the ester and amide peracidprecursors have alkyl leaving groups ranging in carbon chain lengths ofC1-C8. In each of these aspects, the peroxycarboxylic acid concentrationranges from 0.0001 wt-% to 20 wt-%, preferably from about 0.0001 wt-% to10 wt-%, or from about 0.0001 wt-% to 5 wt-%, or from about 1 wt-% toabout 3 wt-%. Without limiting the scope of invention, the numericranges are inclusive of the numbers defining the range and include eachinteger within the defined range.

In an aspect of the invention, a peroxide-reducing agent is combinedwith a peracid composition. In an aspect, a peracid composition having aconcentration of less than or equal to about 10% may be combined withthe peroxide-reducing agent, without having a detrimental effect on theperoxide-reducing agent. In a further preferred aspect, a peracidcomposition having a concentration of less than or equal to about 5% issuitable for use with the peroxide-reducing agent, without having adetrimental effect on the peroxide-reducing agent. In a still furtherpreferred aspect, a peracid concentration of less than or equal to 3% ispreferred, or less than or equal to 2%. Without limiting the scope ofinvention, the numeric ranges are inclusive of the numbers defining therange and include each integer within the defined range.

Hydrogen Peroxide

The present invention includes reduced amounts of hydrogen peroxide, andpreferably no hydrogen peroxide. Hydrogen peroxide, H₂O₂, provides theadvantages of having a high ratio of active oxygen because of its lowmolecular weight (34.014 g/mole) and being compatible with numeroussubstances that can be treated by methods of the invention because it isa weakly acidic, clear, and colorless liquid. Another advantage ofhydrogen peroxide is that it decomposes into water and oxygen. It isadvantageous to have these decomposition products because they aregenerally compatible with substances being treated. For example, thedecomposition products are generally compatible with metallic substance(e.g., substantially noncorrosive) and are generally innocuous toincidental contact and are environmentally friendly.

In one aspect of the invention, hydrogen peroxide is initially in anantimicrobial peracid composition in an amount effective for maintainingequilibrium between a carboxylic acid, hydrogen peroxide, water and aperacid. The amount of hydrogen peroxide should not exceed an amountthat would adversely affect the antimicrobial activity of a compositionof the invention. In further aspects of the invention, hydrogen peroxideconcentration is significantly reduced within an antimicrobial peracidcomposition, preferably containing hydrogen peroxide at a concentrationas close to zero as possible. That is, the concentration of hydrogenperoxide is minimized, through the use of the selected peroxide-reducingagents according to the invention. In further aspects, the concentrationof hydrogen peroxide is reduced and/or eliminated as a result ofdistilled equilibrium peracid compositions, other catalysts for hydrogenperoxide decomposition (e.g. biomimetic complexes) and/or the use ofperhydrolysis of esters (e.g. triacetin) to obtain peracids with verylow hydrogen peroxide.

According to the invention, an advantage of minimizing the concentrationof hydrogen peroxide is that antimicrobial activity of a composition ofthe invention is improved as compared to conventional equilibriumperacid compositions. Without being limited to a particular theory ofthe invention, significant improvements in antimicrobial efficacy resultfrom enhanced peracid, namely POAA stability from the reduced hydrogenperoxide concentration.

In an aspect of the invention, hydrogen peroxide can typically bepresent in a use solution in an amount less than 2500 ppm, preferablyless than 2000 ppm, more preferably less than 1000 ppm. In preferredembodiments, the use of a catalase reduces the hydrogen peroxideconcentration as close to zero as possible, preferably a concentrationof zero. Without limiting the scope of invention, the numeric ranges areinclusive of the numbers defining the range and include each integerwithin the defined range.

In further aspects of the invention, hydrogen peroxide in a peracidcomposition is reduced by at least 50%, at least 60%, at least 70%, atleast 80%, or at least 90%. Preferably the hydrogen peroxide issubstantially zero after the treatment of a peracid compositionaccording to the invention. In additional aspects, the ratio of hydrogenperoxide to peracid in a concentrated composition for use according tothe invention is from about 0:100 to about 1:10, preferably from about0.5:100 to about 0.5:10. Various concentrated peracid compositions witha hydrogen peroxide to peracid ratio from about 0:100 to about 1:10,preferably from about 0.5:100 to about 0.5:10, may be employed toproduce a use solution for treatment according to the invention. Withoutlimiting the scope of invention, the numeric ranges are inclusive of thenumbers defining the range and include each integer within the definedrange.

In a further aspect, a use solution may have a ratio of hydrogenperoxide to peracid as low as from about 0.001 part hydrogen peroxide toabout 1 part peracid. Preferably, any ratio wherein the amount ofhydrogen peroxide is less than peracid is suitable for use according tothe invention in formulating a use solution for water treatments.Without limiting the scope of invention, the numeric ranges areinclusive of the numbers defining the range and include each integerwithin the defined range.

Carboxylic Acid

The present invention includes a carboxylic acid with the peracidcomposition and hydrogen peroxide. A carboxylic acid includes anycompound of the formula R—(COOH)_(n) in which R can be hydrogen, alkyl,alkenyl, alkyne, acylic, alicyclic group, aryl, heteroaryl, orheterocylic group, and n is 1, 2, or 3. Preferably R includes hydrogen,alkyl, or alkenyl. The terms “alkyl,” “alkenyl,” “alkyne,” “acylic,”“alicyclic group,” “aryl,” “heteroaryl,” and “heterocyclic group” are asdefined above with respect to peracids.

Examples of suitable carboxylic acids according to the equilibriumsystems of peracids according to the invention include a varietymonocarboxylic acids, dicarboxylic acids, and tricarboxylic acids.Monocarboxylic acids include, for example, formic acid, acetic acid,propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoicacid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid,dodecanoic acid, glycolic acid, lactic acid, salicylic acid,acetylsalicylic acid, mandelic acid, etc. Dicarboxylic acids include,for example, adipic acid, fumaric acid, glutaric acid, maleic acid,succinic acid, malic acid, tartaric acid, etc. Tricarboxylic acidsinclude, for example, citric acid, trimellitic acid, isocitric acid,agaicic acid, etc.

In an aspect of the invention, a particularly well suited carboxylicacid is water soluble such as formic acid, acetic acid, propionic acid,butanoic acid, lactic acid, glycolic acid, citric acid, mandelic acid,glutaric acid, maleic acid, malic acid, adipic acid, succinic acid,tartaric acid, etc. Preferably a composition of the invention includesacetic acid, octanoic acid, or propionic acid, lactic acid, heptanoicacid, octanoic acid, or nonanoic acid. Additional examples of suitablecarboxylic acids are employed in sulfoperoxycarboxylic acid orsulfonated peracid systems, which are disclosed in U.S. Pat. No.8,344,026, and U.S. Patent Publication Nos. 2010/0048730 and2012/0052134, each of which are herein incorporated by reference intheir entirety.

Any suitable C₁-C₂₂ carboxylic acid can be used in the presentcompositions. In some embodiments, the C₁-C₂₂ carboxylic acid is aC₂-C₂₀carboxylic acid. In other embodiments, the C₁-C₂₂ carboxylic acidis a C₁, C₂, C₃, C₄, C₅, C₆, C₇, C₈, C₉, C₁₀, C₁₁, C₁₂, C₁₃, C₁₄, C₁₅,C₁₆, C₁₇, C₁₈, C₁₉, C₂₀, C₂₁, or C₂₂ carboxylic acid. In still otherembodiments, the C₁-C₂₂ carboxylic acid comprises acetic acid, octanoicacid and/or sulfonated oleic acid.

In an aspect of the invention, a carboxylic acid is present in a usesolution with the water source in need of treatment in an amount ofbetween about 1 ppm and about 5000 ppm, preferably between about 1 ppmand about 2000 ppm, preferably between about 1 ppm and about 1000 ppm,and more preferably between about 1 ppm and about 100 ppm. Withoutlimiting the scope of invention, the numeric ranges are inclusive of thenumbers defining the range and include each integer within the definedrange. The amount of carboxylic acid above the preferred range of 100ppm may be employed for highly contaminated waters in need of treatment,such as source waters including increased amounts of produced water(e.g. recycled waters).

Additional Optional Materials

The composition can optionally include additional ingredients to enhancethe composition for water treatment according to the invention,including for example, friction reducers, viscosity enhancers and thelike. Additional optional functional ingredients may include forexample, peracid stabilizers, emulsifiers, corrosion inhibitors and/ordescaling agents (i.e. scale inhibitors), surfactants and/or additionalantimicrobial agents for enhanced efficacy (e.g. mixed peracids,biocides), antifoaming agents, acidulants (e.g. strong mineral acids) orother pH modifiers, additional carboxylic acids, and the like. In anembodiment, no additional functional ingredients are employed.

Friction Reducers

Friction reducers are used in water or other water-based fluids used inhydraulic fracturing treatments for subterranean well formations inorder to improve permeability of the desired gas and/or oil beingrecovered from the fluid-conductive cracks or pathways created throughthe fracking process. The friction reducers allow the water to be pumpedinto the formations more quickly. Various polymer additives have beenwidely used as friction reducers to enhance or modify thecharacteristics of the aqueous fluids used in well drilling, recoveryand production applications.

Examples of commonly used friction reducers include polyacrylamidepolymers and copolymers. In an aspect, additional suitable frictionreducers may include acrylamide-derived polymers and copolymers, such aspolyacrylamide (sometime abbreviated as PAM), acrylamide-acrylate(acrylic acid) copolymers, acrylic acid-methacrylamide copolymers,partially hydrolyzed polyacrylamide copolymers (PHPA), partiallyhydrolyzed polymethacrylamide, acrylamide-methyl-propane sulfonatecopolymers (AMPS) and the like. Various derivatives of such polymers andcopolymers, e.g., quaternary amine salts, hydrolyzed versions, and thelike, should be understood to be included with the polymers andcopolymers described herein.

Friction reducers are combined with water and/or other aqueous fluids,which in combination are often referred to as “slick water” fluids.Slick water fluids have reduced frictional drag and beneficial flowcharacteristics which enable the pumping of the aqueous fluids intovarious gas- and/or oil-producing areas, including for example forfracturing.

In an aspect of the invention, a friction reducer is present in a usesolution in an amount between about 100 ppm to 1000 ppm. In a furtheraspect, a friction reducer is present in a use solution in an amount ofat least about 0.01 wt-% to about 10 wt-%, preferably at least about0.01 wt-% to about 5 wt-%, preferably at least about 0.01 wt-% to about1 wt-%, more preferably at least about 0.01 wt-% to about 0.5 wt-%, andstill more preferably at least about 0.01 wt-% to about 0.1 wt-%.Without limiting the scope of invention, the numeric ranges areinclusive of the numbers defining the range and include each integerwithin the defined range.

Beneficially, the compositions and methods of the invention do notnegatively interfere with friction reducers included in an aqueoussolution. Without being limited to a particular theory of the invention,it is thought that the reduction and/or elimination of the oxidanthydrogen peroxide from the peracid composition promotes the stabilityand efficacy of any variation in the amount of friction reducer presentin a use solution.

Viscosity Enhancers

Viscosity enhancers are additional polymers used in water or otherwater-based fluids used in hydraulic fracturing treatments to provideviscosity enhancement. Natural and/or synthetic viscosity-increasingpolymers may be employed in compositions and methods according to theinvention. Viscosity enhancers may also be referred to as gelling agentsand examples include guar, xanthan, cellulose derivatives andpolyacrylamide and polyacrylate polymers and copolymers, and the like.

In an aspect of the invention, a viscosity enhancer is present in a usesolution in an amount between about 100 ppm to 1000 ppm. In a furtheraspect, a viscosity enhancer is present in a use solution in an amountof at least about 0.01 wt-% to about 10 wt-%, preferably at least about0.01 wt-% to about 5 wt-%, preferably at least about 0.01 wt-% to about1 wt-%, at least about 0.01 wt-% to about 2 wt-%, preferably at leastabout 0.01 wt-% to about 1 wt-%, preferably at least about 0.01 wt-% toabout 0.5 wt-%. Without limiting the scope of invention, the numericranges are inclusive of the numbers defining the range and include eachinteger within the defined range.

Beneficially, the compositions and methods of the invention do notnegatively interfere with viscosity enhancer included in an aqueoussolution. Without being limited to a particular theory of the invention,it is believed the reduction and/or elimination of the oxidant hydrogenperoxide from the peracid composition promotes the stability andefficacy of any variation in the amount of viscosity enhancer present ina use solution.

Corrosion Inhibitors

Corrosion inhibitors are additional molecules used in oil and gasrecovery operations. Corrosion inhibitors that may be employed in thepresent disclosure are disclosed in U.S. Pat. No. 5,965,785, U.S. PatentPublication No. 2010/0108566, GB Patent No. 1,198,734, WO/03/006581,WO04/044266, and WO08/005058, each of which are incorporated herein byreference in their entirety.

In an aspect of the invention, a corrosion inhibitor is present in a usesolution in an amount between about 100 ppm to 1000 ppm. In a furtheraspect, a corrosion inhibitor is present in a use solution in an amountof at least about 0.0001 wt-% to about 10 wt-%, preferably at leastabout 0.0001 wt-% to about 5 wt-%, preferably at least about 0.0001 wt-%to about 1 wt-%, preferably at least about 0.0001 wt-% to about 0.1wt-%, and still more preferably at least about 0.0001 wt-% to about 0.05wt-%. Without limiting the scope of invention, the numeric ranges areinclusive of the numbers defining the range and include each integerwithin the defined range.

Beneficially, the compositions and methods of the invention do notnegatively interfere with corrosion inhibitor included in an aqueoussolution. Without being limited to a particular theory of the invention,it is believed the reduction and/or elimination of the oxidant hydrogenperoxide from the peracid composition promotes the stability andefficacy of any variation in the amount of corrosion inhibitor presentin a use solution.

Scale Inhibitors

Scale inhibitors are additional molecules used in oil and gas recoveryoperations. Common scale inhibitors that may be employed in these typesof applications include polymers and co-polymers, phosphates, phosphateesters and the like.

In an aspect of the invention, a scale inhibitor is present in a usesolution in an amount between about 100 ppm to 1000 ppm. In a furtheraspect, a scale inhibitor is present in a use solution in an amount ofat least about 0.0001 wt-% to about 10 wt-%, at least about 0.0001 wt-%to about 1 wt-%, preferably at least about 0.0001 wt-% to about 0.1wt-%, preferably at least about 0.0001 wt-% to about 0.05 wt-%. Withoutlimiting the scope of invention, the numeric ranges are inclusive of thenumbers defining the range and include each integer within the definedrange.

Beneficially, the compositions and methods of the invention do notnegatively interfere with scale inhibitor included in an aqueoussolution. Without being limited to a particular theory of the invention,it is thought that the reduction and/or elimination of the oxidanthydrogen peroxide from the peracid composition promote the stability andefficacy of any variation in the amount of scale inhibitor present in ause solution.

Additional Antimicrobial Agents

Additional antimicrobial agents may be included in the compositionsand/or methods of the invention for enhanced antimicrobial efficacy. Inaddition to the use of mixed peracid compositions, additionalantimicrobial agents (e.g. surfactants) and biocides may be employed.Additional biocides may include, for example, a quaternary ammoniumcompound as disclosed in U.S. Pat. No. 6,627,657, which is incorporatedherein by reference in its entirety. Beneficially, the presence of thequaternary ammonium compound provides both synergistic antimicrobialefficacies with peracids, as well as maintains long term biocidalefficacy of the compositions.

In another embodiment, the additional biocide may include an oxidizercompatible phosphonium biocide, such as tributyl tetradecyl phosphoniumchloride. The phosphonium biocide provides similar antimicrobialadvantages as the quaternary ammonium compound in combination with theperacids. In addition, the phosphonium biocide is compatible with theanionic polymeric chemicals commonly used in the oil field applications,such as the methods of the fracking disclosed according to theinvention.

Additional antimicrobial and biocide agents may be employed in amountssufficient to provide antimicrobial efficacy, as may vary depending uponthe water source in need of treatment and the contaminants therein. Suchagents may be present in a use solution in an amount of at least about0.1 wt-% to about 50 wt-%, preferably at least about 0.1 wt-% to about20 wt-%, more preferably from about 0.1 wt-% to about 10 wt-%. Withoutlimiting the scope of invention, the numeric ranges are inclusive of thenumbers defining the range and include each integer within the definedrange.

Acidulants

Acidulants may be included as additional functional ingredients in acomposition according to the invention. In an aspect, a strong,oxidative mineral acid such as nitric acid or sulfuric acid can be usedto treat water sources, as disclosed in U.S. Pat. No. 4,587,264, whichis incorporated herein by reference in its entirety. For example, thecombined use of a strong mineral acid with the peracid compositionprovides enhanced antimicrobial efficacy as a result of the acidityassisting in removing chemical contaminants within the water source(e.g. sulfite and sulfide species). In an aspect of the invention, theuse of an acidulant, such as a mineral acid, is suitable for decreasingthe pH of the water source and/or the treated peracid composition toobtain additional and/or synergistic impact on cleaning efficacy.

In an aspect, an acidulant may be used to decrease the pH of the watersource in need of treatment to a pH below about 6, preferably belowabout 5, and more preferably between about 4.5 and about 5.5 to get asynergistic impact on water clean-up from the acid. In a preferredaspect, an acidulant is used to decrease the pH of the treated watersource from about 2 to about 6 to provide a synergistic impact on waterclean-up. According to such an embodiment, any acidulant may be employedto decrease the pH of the water source. Examples of suitable acidulantsinclude hydrochloric acid and other acids, and chlorine, chlorinedioxide (ClO₂) and other oxidants.

In addition, some strong mineral acids, such as nitric acid, provide afurther benefit of reducing the risk of corrosion toward metalscontacted by the peracid compositions according to the invention.Exemplary peracid products containing nitric acid are commerciallyavailable from Enviro Tech Chemical Services, Inc. (Reflex brand) andfrom Solvay Chemicals (Proxitane® NT brand).

In a still further aspect, an acidulant may be employed to decrease thepH of the peracid composition according to the invention to increase theperacid stability by decreasing the pH of the peracid composition. Forexample, in some embodiments decreasing the pH of the treated peracidcomposition from about 8 or greater to less than about 8, or less thanabout 7.5, or less than about 7 has a beneficial impact on the peracidstability for use according to the methods of the invention.

Acidulants may be employed in amounts sufficient to provide the intendedantimicrobial efficacy, peracid stability and/or anticorrosion benefits,as may vary depending upon the peracid composition and/or water sourcein need of treatment and the contaminants therein. Such agents may bepresent in a use solution in an amount of at least about 0.1 wt-% toabout 50 wt-%, preferably at least about 0.1 wt-% to about 20 wt-%, morepreferably from about 0.1 wt-% to about 10 wt-%. Without limiting thescope of invention, the numeric ranges are inclusive of the numbersdefining the range and include each integer within the defined range.

Peracid Stabilizers

In some embodiments, the compositions of the present invention includeone or more stabilizing agents. The stabilizing agents can be used, forexample, to stabilize the peracid and hydrogen peroxide and prevent thepremature oxidation of this constituent within the composition of theinvention.

In some embodiments, an acidic stabilizing agent can be used. Thus, insome embodiments, the compositions of the present invention can besubstantially free of an additional acidulant.

Suitable stabilizing agents include, for example, chelating agents orsequestrants. Suitable sequestrants include, but are not limited to,organic chelating compounds that sequester metal ions in solution,particularly transition metal ions. Such sequestrants include organicamino- or hydroxy-polyphosphonic acid complexing agents (either in acidor soluble salt forms), carboxylic acids (e.g., polymericpolycarboxylate), hydroxycarboxylic acids, aminocarboxylic acids, orheterocyclic carboxylic acids, e.g., pyridine-2,6-dicarboxylic acid(dipicolinic acid).

In some embodiments, the compositions of the present invention includedipicolinic acid as a stabilizing agent. Compositions includingdipicolinic acid can be formulated to be free or substantially free ofphosphorous.

In other embodiments, the sequestrant can be or include phosphonic acidor phosphonate salt. Suitable phosphonic acids and phosphonate saltsinclude HEDP; ethylenediamine tetrakis methylenephosphonic acid (EDTMP);diethylenetriamine pentakis methylenephosphonic acid (DTPMP);cyclohexane-1,2-tetramethylene phosphonic acid; amino[tri(methylenephosphonic acid)]; (ethylene diamine[tetra methylene-phosphonic acid)];2-phosphene butane-1,2,4-tricarboxylic acid; or salts thereof, such asthe alkali metal salts, ammonium salts, or alkyloyl amine salts, such asmono, di, or tetra-ethanolamine salts; picolinic, dipicolinic acid ormixtures thereof. In some embodiments, organic phosphonates, e.g., HEDPare included in the compositions of the present invention.

Commercially available food additive chelating agents includephosphonates sold under the trade name DEQUEST® including, for example,1-hydroxyethylidene-1,1-diphosphonic acid, available from MonsantoIndustrial Chemicals Co., St. Louis, Mo., as DEQUEST® 2010;amino(tri(methylenephosphonic acid)), (N[CH₂PO₃H₂]₃), available fromMonsanto as DEQUEST® 2000; ethylenediamine[tetra(methylenephosphonicacid)] available from Monsanto as DEQUEST® 2041; and2-phosphonobutane-1,2,4-tricarboxylic acid available from Mobay ChemicalCorporation, Inorganic Chemicals Division, Pittsburgh, Pa., as BayhibitAM.

The sequestrant can be or include aminocarboxylic acid type sequestrant.Suitable aminocarboxylic acid type sequestrants include the acids oralkali metal salts thereof, e.g., amino acetates and salts thereof.Suitable aminocarboxylates include N-hydroxyethy laminodiacetic acid;hydroxyethylenediaminetetraacetic acid, nitrilotriacetic acid (NTA);ethylenediaminetetraacetic acid (EDTA); N-hydroxyethyl-ethylenediaminetriacetic acid (HEDTA); diethylenetriaminepentaacetic acid(DTPA); and alanine-N,N-diacetic acid; and the like; and mixturesthereof.

The sequestrant can be or include a polycarboxylate. Suitablepolycarboxylates include, for example, polyacrylic acid, maleic/olefincopolymer, acrylic/maleic copolymer, polymethacrylic acid, acrylicacid-methacrylic acid copolymers, hydrolyzed polyacrylamide, hydrolyzedpolymethacrylamide, hydrolyzed polyamide-methacrylamide copolymers,hydrolyzed polyacrylonitrile, hydrolyzed polymethacrylonitrile,hydrolyzed acrylonitrile-methacrylonitrile copolymers, polymaleic acid,polyfumaric acid, copolymers of acrylic and itaconic acid, phosphinopolycarboxylate, acid or salt forms thereof, mixtures thereof, and thelike.

In certain embodiments, the present composition includes about 0.01 toabout 10 wt-% stabilizing agent, about 0.4 to about 4 wt-% stabilizingagent, about 0.6 to about 3 wt-% stabilizing agent, about 1 to about 2wt-% stabilizing agent. It is to be understood that all values andranges within these values and ranges are encompassed by the presentinvention.

Methods of Use

In some aspects, the methods disclosed for water treatment in oil andgas recovery provide effective antimicrobial efficacy without anydeleterious interaction with functional agents, including for examplefriction reducers. In a further aspect, the methods for water treatmentaccording to the invention using the peroxide-reducing agent provideincreased antimicrobial efficacy compared to the use of theantimicrobial peracids alone. In a still further aspect, the methods ofuse result in the disposal of cleaner water with low numbers ofmicroorganisms. In yet a still further aspect of the methods of theinvention, the reduction and/or elimination of H₂O₂ from the peracidcompositions minimizes the negative effects of the oxidant H₂O₂.

Use in Water Treatment

The treated peracid compositions (i.e. reduced or no hydrogen peroxideperacid compositions) can be used for a variety of industrialapplications, e.g., to reduce microbial or viral populations on asurface or object or in a body or stream of water. In some aspects, theinvention includes methods of using the treated peracid compositions toprevent biological fouling in various industrial processes andindustries, including oil and gas operations, to control microorganismgrowth, eliminate microbial contamination, limit or prevent biologicalfouling in liquid systems, process waters or on the surfaces ofequipment that come in contact with such liquid systems. As referred toherein, microbial contamination can occur in various industrial liquidsystems including, but not limited to, air-borne contamination, watermake-up, process leaks and improperly cleaned equipment. In anotheraspect, the peracid and peroxide-reducing enzyme agent (e.g. catalase)compositions (or other treated peracid compositions having low tosubstantially no hydrogen peroxide) are used to control the growth ofmicroorganisms in water used in various oil and gas operations. In afurther aspect, the compositions are suitable for incorporating intofracturing fluids to control or eliminate microorganisms.

As used herein for the methods of the invention, treated peracidcompositions can employ a variety of peracid compositions having a lowto substantially no hydrogen peroxide concentration. These treatedperacid compositions include peracid compositions with aperoxide-reducing agent to reduce the hydrogen peroxide to peracid ratioand/or other reduced hydrogen peroxide peracid compositions disclosedherein. In a preferred embodiment, peracid and peroxide-reducing agentuse solutions having reduced or substantially no hydrogen peroxide areintroduced to a water source in need of treatment.

The methods by which the treated peracid use solutions are introducedinto the aqueous fluids according to the invention are not critical.Introduction of the treated peracid compositions (and/or introduction ofthe two or more part system, such as a peracid composition and aperoxide-reducing agent composition, may be carried out in a continuousor intermittent manner and will depend on the type of water beingtreated.

In an aspect, treated peracid use solutions are employed according tothe methods of the invention. As referred to herein, treated peracidcompositions or treated peracid use solutions are understood to refer toperacid compositions having reduced or substantially no hydrogenperoxide. Such reduced or substantially no hydrogen peroxide peracidcompositions may be generated by use of peroxide-reducing agent(s) at apoint of use (e.g. combining more than one component part of thecomposition—e.g. the peroxide-reducing agent and a peracid compositionin a two part system) and/or generated prior to a point of use.

In an aspect, the treated peracid compositions are generated at a pointof use, and may be generated within a water source on site. In anaspect, the peracid composition and a peroxide-reducing agent, such as ametal and/or strong oxidizing agent, are combined with a water source ata point of use and the hydrogen peroxide concentration of the usesolution is reduced within a period of time from at least a minute to afew hours, preferably from at least 5 minutes to a few hours. Oneskilled in the art will ascertain that the treatment time for a usesolution of a peracid composition within a water source to be treatedwill vary depending upon the concentration of the peroxide-reducingagent and/or the volume of the peracid composition and/or water sourcein need of treatment. The concentrations of the peracid composition andperoxide-reducing agent will further vary depending upon the amount ofbacteria within the water source in need of treatment.

In an aspect, the treated peracid use solutions are added to waters inneed of treatment prior to the drilling and fracking steps in order torestrict the introduction of microbes into the reservoir and to preventthe microbes from having a negative effect on the integrity of thefluids. The treatment of source waters (e.g. pond, holding tank, lake,municipal, etc.) and/or produced waters is particularly well suited foruse according to the invention.

The treated waters according to the invention can be used for both slickwater fracturing (i.e. using frictions reducers) and/or gel fracturing(i.e. using viscosity enhancers), depending on the type of formationbeing fractured and the type of hydrocarbon expected to be produced. Useof a treated peracid use solution, namely a peroxide-reducing agenttreated peracid composition use solution having low to substantially nohydrogen peroxide, is suitable for both slick water fracturing and gelfracturing.

In an aspect, pretreating the peracid composition, such as peraceticacid (including a mixture of acetic acid, hydrogen peroxide and water)with a peroxide-reducing agent substantially removes the hydrogenperoxide with minimal to no impact on the fracturing fluids and the wellitself. In an aspect, the peracetic acid pretreated with aperoxide-reducing agent allows the formation of gel suitable for gelfracturing, as opposed to untreated peracetic acid/hydrogen peroxidesolutions that do not allow a gel to form. In a further aspect, thetreated peracid use solutions are added to waters in need of treatmentin the subterranean well formations (e.g. introduced through a bore holein a subterranean formation). These methods provide additional controlwithin the well formation suitable for reducing microbial populationsalready present within the down hole tubing in the well or within thereservoir itself.

In a still further aspect, the treated peracid use solutions are addedto waters in need of treatment before disposal. In such an aspect, flowback waters (e.g. post fracking) are treated to minimize microbialcontaminations in the waters and to remove solids prior to disposal ofthe water into a subterranean well, reuse in a subsequent fracturingapplication or return of the water into local environmental watersources.

In a still further aspect, the treated peracid use solutions are addedto waters in need of treatment before disposal. In such an aspect, flowback waters (e.g. post fracking) are treated to minimize microbialcontaminations in the waters and to remove solids prior to disposal ofthe water into a subterranean well, reuse in a subsequent fracturingapplication or return of the water into local environmental watersources.

In an alternative aspect, the treated peracid use solution may be formedwithin the water source to be treated. For example, a peracidcomposition is provided to a water source and a peroxide-reducing agentis thereafter provided to the water source, such that the reductionand/or elimination of peroxide concentration occur within the watersource. These methods provide additional control within the wellformation suitable for reducing microbial populations already presentwithin the down hole tubing in the well or within the reservoir itself.

In an aspect of the invention, the methods of treating a water sourcemay include the cyclical dosing of treated (e.g. low or no hydrogenperoxide) peracid compositions to a water source. In an alternativeaspect, the methods of treating a water source may include the cyclicaldosing of a water source with a two (or more) part composition used togenerate the treated (e.g. low or no hydrogen peroxide) peracidcomposition within the water source in need of treatment. Such cyclicaldosing may include daily dosing, every two or more day dosing, everythree or more day dosing, every four or more day dosing, every five ormore day dosing, every six or more day dosing, weekly dosing, or longerfrequency dosing. In a preferred aspect, the water source is treated inan every five day cycle for optimal reduction or elimination of hydrogenperoxide within a peracid composition used to treat the water source.Without being limited according to the mechanism and/or the scope of theinvention, all ranges of the dosing cycles are included within the scopeof the invention. In an aspect, the present invention is directed to amethod for treating water, which method comprises providing the abovecompositions to a water source in need of treatment to form a treatedwater source, wherein said treated water source comprises from about 1ppm to about 1,000 ppm of said C₁-C₂₂ percarboxylic acid. Any suitableC₁-C₂₂ percarboxylic acid can be used in the present methods. Forexample, peroxyacetic acid, peroxyoctanoic acid and/or peroxysulfonatedoleic acid can be used. In some embodiments, a combination ofperoxyacetic acid, peroxyoctanoic acid and peroxysulfonated oleic acidis used.

The treated peracid composition provides a water source with anysuitable concentration of the hydrogen peroxide. In some embodiments,the treated water source comprises from about 1 ppm to about 15 ppm ofthe hydrogen peroxide. In other embodiments, the treated water sourcecomprises about 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm, 8 ppm,9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm, or 15 ppm of the hydrogenperoxide.

In an aspect, the treated peracid use solutions may be added to anincoming stream of water, such as water added to a holding tank or otherstorage reservoir. In an embodiment, the treated peracid use solutionsare added to provide a peracid concentration (e.g. peracetic acid)applied at a rate of about 1 ppm to about 5000 ppm peracid, from about 1ppm to about 2000 ppm, from about 1 ppm to about 1000 ppm, from about 1ppm to about 500 ppm, and preferably from about 1 ppm to about 100 ppmperacid. Without being limited according to the mechanism and/or thescope of the invention, all ranges are included within the scope of theinvention.

In an alternative aspect, the treated peracid use solutions may be addedat an elevated peracid concentration (e.g. about 200 to about 5000 ppm)to an intermittent water source (e.g. a smaller holding tank, such as upto about 1000 gallons of water) prior to dilution within a largerholding tank or other storage reservoir for a water source (e.g. 1million gallons of water or more). Upon such dilution within a largerwater source the peracid becomes quickly diluted to the preferred rateof about 0.1 ppm to about 100 ppm peracid, preferably from about 1 ppmto about 100 ppm peracid. Without being limited to a mechanism ofaction, such a method beneficially provides a rapid kill ofmicroorganisms within a controlled/smaller volume of a water source inneed of treatment, while still providing a static or slowerantimicrobial activity within a bulk water system. In a still furtheralternative aspect, the treated peracid use solutions may be added to alarger bulk fluid, such as the holding tank or other storage reservoirfor a water source. For example, in some aspects, a bulk fluid sourcemay be a holding tank or other storage reservoir having a volume fromabout 1000 gallons to about 20 million gallons or more, preferably fromabout 1000 gallons to about 12 million gallons. In such an embodiment,the treated peracid use solutions provide a peracid concentration (e.g.peracetic acid) in the bulk water source from 0.1 ppm to about 100 ppmperacid or greater, preferably from about 1 ppm to about 100 ppm peracidor greater. Without being limited according to the mechanism and/or thescope of the invention, all ranges are included within the scope of theinvention.

According to the various aspects of the invention, monitoring devicesand/or means may be included to measure the application rate and/or bulksolution of peracid in order to ensure either the application rate ofperacid (or the bulk solution having a maintained peracid) at aconcentration of from 0.1 ppm to about 100 ppm peracid or greater,preferably from about 1 ppm to about 100 ppm peracid or greater.

In an aspect, the treated peracid use solutions may be added to dormantwater sources. As one skilled in the art will ascertain, the use oftreated peracid use solutions in dormant water sources will oftenrequire less frequent dosing that other water sources. For example, useof the treated water sources during non-pumping (e.g. non-use) periods,such as for example winter, will require less frequent dosing due to themore static nature of the water source at that particular time.

In a still further aspect, the treated peracid use solutions are addedto waters in need of treatment before disposal. In such an aspect, flowback waters (e.g. post fracking) are treated to minimize microbialcontaminations in the waters and to remove solids prior to disposal ofthe water into a subterranean well, reuse in a subsequent fracturingapplication or return of the water into local environmental watersources. Such flow back waters may be held, for example, in tanks, pondsor the like, in some aspects of the invention.

In an aspect, the water source in need of treatment may varysignificantly. For example, the water source may be a freshwater source(e.g. pond water), salt water or brine source, brackish water source,recycled water source, or the like. In an aspect, wherein offshore welldrilling operations are involved, seawater sources are often employed(e.g. saltwater or non-saltwater). Beneficially, the peracid andperoxide-reducing agent compositions of the invention are suitable foruse with any types of water and provide effective antimicrobialefficiency with any of such water sources.

Large volumes of water are employed according to the invention asrequired in well fluid operations. As a result, in an aspect of theinvention, recycled water sources (e.g. produced waters) are oftenemployed to reduce the amount of a freshwater, pond water or seawatersource required. Recycled or produced water are understood to includenon-potable water sources. The use of such produced waters (incombination with freshwater, pond water or seawater) reduces certaineconomic and/or environmental constraints. In an aspect of theinvention, thousands to millions of gallons of water may be employed andthe combination of produced water with fresh water sources providessignificant economic and environmental advantages.

In an aspect of the invention, as much produced water as practical isemployed. In an embodiment at least 1% produced water is employed,preferably at least 5% produced water is employed, preferably at least10% produced water is employed, preferably at least 20% produced wateris employed, or more preferably more than 20% produced water isemployed. Without being limited according to the mechanism and/or thescope of the invention, all ranges are included within the scope of theinvention.

The treated water source can comprise any suitable concentration of theC₁-C₂₂ percarboxylic acid. In some embodiments, the treated water sourcecomprises from about 10 ppm to about 200 ppm of the C₁-C₂₂ percarboxylicacid. In other embodiments, the treated water source comprises about 1ppm, 10 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700ppm, 800 ppm, 900 ppm or 1,000 ppm of the C₁-C₂₂ percarboxylic acid. Thepresent methods can be used to treat any suitable or desirable watersources. In another example, the present methods can be used to treatfresh water, pond water, sea water, produced water and a combinationthereof. In some embodiments, the water source comprises at least about1 wt-% produced water. In other embodiments, the water source comprisesat least about 1 wt-%, 2 wt-%, 3 wt-%, 4 wt-%, 5 wt-%, 6 wt-%, 7 wt-%, 8wt-%, 9 wt-%, or 10 wt-%, 15 wt-%, 20 wt-%, 25 wt-%, 30 wt-% or moreproduced water.

In an aspect of the invention, the method includes a pretreatment step,wherein the peracid composition is treated with a peroxide-reducingagent to reduce the hydrogen peroxide concentration in a use solution.The pretreatment step occurs prior to combining the peracidantimicrobial composition and/or peroxide-reducing agent to a watersource in need of treatment. In an aspect of the invention, thepretreatment may occur within a few minutes to hours before addition toa water source. Preferably, a commercial peracid formulation is employed(e.g. peracetic acid). Thereafter, the peracid and peroxide-reducingagent composition use solution may be diluted to obtain the desiredperacetic acid concentrations, with low and/or no hydrogen peroxideconcentration.

According to embodiments of the invention, a sufficient amount of thepretreated peracid and peroxide-reducing agent use solution compositionis added to the aqueous water source in need of treatment to provide thedesired peracid concentration for antimicrobial efficacy. For example, awater source is dosed amounts of the peracid and peroxide-reducing agentuse solution composition until a peracid concentration within the watersource is detected within the preferred concentration range (e.g. about1 ppm to about 100 ppm peracid). In an aspect, it is preferred to have amicrobial count of less than about 100,000 microbes/mL, more preferablyless than about 10,000 microbes/mL, or more preferably less than about1,000 microbes/mL. Without being limited according to the mechanismand/or the scope of the invention, all ranges are included within thescope of the invention.

In some embodiments, the level of a microorganism, if present in thewater source, is stabilized or reduced by the present methods. Forexample, at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% or moreof the microorganism, if present in the water source, is killed,destroyed, removed and/or inactivated by the present methods. In afurther aspect of the invention, the method includes a pretreatment stepof the water source. In some aspects, the water source in need oftreatment may be first dosed an acidulant to decrease the pH of thewater source. Beneficially, in an aspect of the invention, thepretreatment of a water source with an acidulant provides increasedperacid stability within the water source.

The methods of use as described herein can vary in the temperature andpH conditions associated with use of the aqueous treatment fluids. Forexample, the aqueous treatment fluids may be subjected to varyingambient temperatures according to the applications of use disclosedherein, including ranging from about 0° C. to about 180° C. in thecourse of the treatment operations. Preferably, the temperature range isbetween about 5° C. to about 100° C., more preferably between about 10°C. to about 80° C. Without being limited according to the mechanismand/or the scope of the invention, all ranges are included within thescope of the invention. However, as a majority of the antimicrobialactivity of the compositions of the invention occurs over a short periodof time, the exposure of the compositions to relatively hightemperatures is not a substantial concern.

In addition, the peracid composition aqueous treatment fluids (i.e. usesolutions) may be subjected to varying pH ranges, such as from 1 toabout 10.5. Preferably, the pH range is less than about 9, less thanabout 8.2 (pKa value of the representative peracid peracetic acid) toensure the effective antimicrobial efficacy of the peracid. In someaspects of the invention, a pH modifier (such as an acidulant) is addedto a water source in need of treatment according to the invention. Insome embodiments it may be desirable to decrease the pH to between about5 and about 8.5. Without being limited according to the mechanism and/orthe scope of the invention, all ranges are included within the scope ofthe invention.

The antimicrobial compositions of the invention are fast-acting.However, the present methods require a certain minimal contact time ofthe compositions with the water in need of treatment for occurrence ofsufficient antimicrobial effect. The contact time can vary withconcentration of the use compositions, method of applying the usecompositions, temperature of the use compositions, pH of the usecompositions, amount of water to be treated, amount of soil orsubstrates in the water to be treated, or the like. The contact orexposure time can be at least about 15 seconds. In some embodiments, theexposure time is about 1 to 5 minutes. In other embodiments, theexposure time is at least about 10 minutes, 30 minutes, or 60 minutes.In other embodiments, the exposure time is a few minutes to hours. Inother embodiments, the exposure time is a few days or more.Beneficially, the compositions for use according to the invention aresuitable for short contact times due in part to the non-oxidizing natureof the compositions having reduced or eliminated hydrogen peroxidecontent. The contact time will further vary based upon the concentrationof peracid in a use solution.

In further aspects of the invention, the methods include the directionof the treated water compositions into a subterranean environment and/ora well-bore. In some aspects, the treated water compositions aredirected into a subterranean environment and/or a well-bore at a speedfaster than about 30 barrel (bbl.)/minute, faster than about 60 barrel(bbl.)/minute, and/or at a speed of about 65 barrel (bbl.)/minute andabout 100 barrel (bbl.)/minute. Without being limited according to themechanism and/or the scope of the invention, all ranges are includedwithin the scope of the invention. As referred to herein, a subterraneanenvironment may include, for example, a shale gas reservoir, a well,and/or an oil reservoir.

Beneficial Effects of the Methods of Use in Water Treatment

In some aspects, the methods disclosed for water treatment in oil andgas recovery provide effective antimicrobial efficacy withoutdeleterious interaction with functional agents, including for examplefriction reducers. In a further aspect, the methods for water treatmentprovide increased antimicrobial efficacy compared to the use of theantimicrobial peracids alone. In a still further aspect, the methods ofuse result in the disposal of cleaner water with low numbers ofmicroorganisms. In yet a further aspect of the methods of the invention,the reduction and/or elimination of H₂O₂ from the peracid compositionsminimizes the negative effects of the oxidant H₂O₂.

In an aspect, the methods of use provide an antimicrobial for use thatdoes not negatively impact the environment. Beneficially, thedegradation of the compositions of the invention provides a “green”alternative. In an aspect of the invention, utilizing peroxyacetic acidis beneficial as the by-products are non-toxic, non-persistent in theenvironment, certified as organic and permitted for discharge in surfacewaters.

In a further aspect, the methods of use provide an antimicrobial for usethat does not negatively interfere with friction reducers, viscosityenhancers and/or other functional ingredients. In a further aspect, themethods of use do not negatively interfere with any additionalfunctional agents utilized in the water treatment methods, including forexample, corrosion inhibitors, descaling agents, and the like. Thecompositions administered according to the invention provide extremelyeffective control of microorganisms without adversely affecting thefunctional properties of any additive polymers of an aqueous system. Inaddition, the treated peracid composition use solutions provideadditional benefits to a system, including for example, reducingcorrosion within the system due to the decreased or substantiallyeliminated hydrogen peroxide from a treated peracid composition.Beneficially, the non-deleterious effects of the treated peracidcompositions (namely using a peroxide-reducing agent) on the variousfunctional ingredients used in water treatment methods are achievedregardless of the make-up of the water source in need of treatment.

In an additional aspect, the methods of use prevent the contamination ofsystems, such as well or reservoir souring. In further aspects, themethods of use prevent microbiologically-influenced corrosion of thesystems upon which it is employed.

In additional aspects of the invention, the reduction and/or eliminationof hydrogen peroxide from the systems reduces volume expansion withinsealed systems (e.g. wells). As a result there is a significantlydecreased or eliminated risk of well blow outs due to the removal ofgases within the antimicrobial compositions used for treating thevarious water sources.

In further aspects, the methods of use employ the antimicrobial and/orbleaching activity of the peracid compositions. For example, theinvention includes a method for reducing a microbial population and/or amethod for bleaching. These methods can operate on an article, surface,in a body or stream of water or a gas, or the like, by contacting thearticle, surface, body, or stream with the compositions. Contacting caninclude any of numerous methods for applying the compositions,including, but not limited to, providing the antimicrobial peracidcompositions in an aqueous use solution and immersing any articles,and/or providing to a water source in need of treatment.

The compositions are suitable for antimicrobial efficacy against a broadspectrum of microorganisms, providing broad spectrum bactericidal andfungistatic activity. For example, the peracid biocides of thisinvention provide broad spectrum activity against wide range ofdifferent types of microorganisms (including both aerobic and anaerobicmicroorganisms), including bacteria, yeasts, molds, fungi, algae, andother problematic microorganisms associated with oil- and gas-fieldoperations.

Exemplary microorganisms susceptible to the peracid compositions of theinvention include, gram positive bacteria (e.g., Staphylococcus aureus,Bacillus species (sp.) like Bacillus subtilis, Clostridia sp.), gramnegative bacteria (e.g., Escherichia coli, Pseudomonas sp., Klebsiellapneumoniae, Legionella pneumophila, Enterobacter sp., Serratia sp.,Desulfovibrio sp., and Desulfotomaculum sp.), yeasts (e.g.,Saccharomyces cerevisiae and Candida albicans), molds (e.g., Aspergillusniger, Cephalosporium acremonium, Penicillium notatum, and Aureobasidiumpullulans), filamentous fungi (e.g., Aspergillus niger and Cladosporiumresinae), algae (e.g., Chlorella vulgaris, Euglena gracilis, andSelenastrum capricornutum), and other analogous microorganisms andunicellular organisms (e.g., phytoplankton and protozoa).

Use in Other Treatments

Additional embodiments of the invention include water treatments forvarious industrial processes for treating liquid systems. As usedherein, “liquid system” refers to flood waters or an environment withinat least one artificial artifact, containing a substantial amount ofliquid that is capable of undergoing biological fouling. Liquid systemsinclude but are not limited to industrial liquid systems, industrialwater systems, liquid process streams, industrial liquid processstreams, industrial process water systems, process water applications,process waters, utility waters, water used in manufacturing, water usedin industrial services, aqueous liquid streams, liquid streamscontaining two or more liquid phases, and any combination thereof.

In a further aspect, the compositions and methods can also be used totreat other liquid systems where both the compositions' antimicrobialfunction and oxidant properties can be utilized. Aside from themicrobial issues surrounding waste water, waste water is often rich inmalodorous compounds of reduced sulfur, nitrogen or phosphorous. Astrong oxidant such as the compositions disclosed herein converts thesecompounds efficiently to their odor free derivatives e.g. the sulfates,phosphates and amine oxides. These same properties are very useful inthe pulp and paper industry where the property of bleaching is also ofgreat utility.

In a still further aspect, the compositions and methods can also be usedfor various aseptic treatment uses. Description of various applicationsof use of treated peracid compositions having low or reduced hydrogenperoxide are disclosed for example in U.S. Pat. No. 8,226,939, entitled“Antimicrobial Peracid Compositions with Selected Catalase Enzymes andMethods of Use in Aseptic Packaging,” which is incorporated by referencein its entirety.

In an aspect, aseptic packaging fillers, including both categories: asingle use filler and a re-use or recirculating filler, are suitable forusing the compositions and methods of the invention. The single usesystem makes a dilute stock solution of peracid. It sprays a smallamount of this solution in the inside of a package to sterilize it. Thesolution can be heated at the point of injection or it can be pre-heatedprior to injection into the bottle. In either case the runningconditions (temperature, contact time, and peracid concentration) arechosen so that the bottle is rendered commercially sterile. Aftercontacting in the inside of the bottle, this spent solution drains fromthe bottle and is exported by the filler either to a drain or to otherparts of the machine for environmental antimicrobial treatments ortreatment of the exterior of the bottles. After the bottle has beentreated it will be rinsed with microbial pure water, filled with aliquid food and sealed. All of these steps occur inside of a positivepressure zone inside the filler called the sterile zone. In a re-usefiller, the filler contains a sump of diluted peracid solution. Thissump is held at the desired temperature (40-65° C.). The filler drawsfrom this sump and uses the solution to sterilize both the inside andoutside of the bottles. The solution drains away from the bottles and itis collected and exported back to the same sump from which itoriginated. After the bottle has been treated it will be rinsed withmicrobiologically pure water, filled with a liquid food and sealed. Allof these steps occur inside of a positive pressure zone inside thefiller called a sterile zone.

In a further aspect, the compositions and methods can be used in asepticpackaging, including contacting the container with a compositionaccording to the present invention. Such contacting can be accomplishedusing a spray device or soaking tank or vessel to intimately contact theinside of the container with the composition for sufficient period oftime to clean or reduce the microbial population in the container. Thecontainer is then emptied of the amount of the present composition used.After emptying, the container can then be rinsed with potable water orsterilized water (which can include a rinse additive) and again emptied.After rinsing, the container can be filled with the food. The containeris then sealed, capped or closed and then packed for shipment forultimate sale. Examples of containers that can be filled includepolyethylene terephthalate (PET), high density polyethylene (HDPE),polypropylene (PP), low density polyethylene, polycarbonate (PC), polyvinyl alcohol (PVA), aluminum, single or multilayer films or pouches,paperboard, steel, glass, multilayer bottles, other polymeric packagingmaterial, combinations of these materials in films, pouches, bottle, orother food packaging materials.

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures, embodiments, claims, and examples described herein.Such equivalents are considered to be within the scope of this inventionand covered by the claims appended hereto. The contents of allreferences, patents, and patent applications cited throughout thisapplication are hereby incorporated by reference to the same extent asif each individual publication or patent application was specificallyand individually indicated as incorporated by reference. Allpublications and patent applications in this specification areindicative of the level of ordinary skill in the art to which thisinvention pertains. The invention is further illustrated by thefollowing examples, which should not be construed as further limiting.

EXAMPLES

Embodiments of the present invention are further defined in thefollowing non-limiting Examples. It should be understood that theseExamples, while indicating certain embodiments of the invention, aregiven by way of illustration only. From the above discussion and theseExamples, one skilled in the art can ascertain the essentialcharacteristics of this invention, and without departing from the spiritand scope thereof, can make various changes and modifications of theembodiments of the invention to adapt it to various usages andconditions. Thus, various modifications of the embodiments of theinvention, in addition to those shown and described herein, will beapparent to those skilled in the art from the foregoing description.Such modifications are also intended to fall within the scope of theappended claims.

Example 1

Corrosion test were conducted. Corrosion rates were determined by awheel box test, using bottles on a wheel in an oven. Each bottlecontained a 1018 carbon steel coupon used for weight loss analysis uponcompletion of the test. The test was conducted using produced water(e.g. recycled water) from an oil/gas well and deionized water. The testwas run at room temperature and in triplicates. The average corrosionrates were compared to blank samples (no chemical added). PAA/H₂O₂ wasdosed at 50, 300 and 900 ppm. Catalase was added at 1000 ppm. The testduration was 24 hours.

Results. The results from the corrosion tests for produced and deionizedwater are shown in FIG. 1. For a produced water sample, addition of 1000ppm catalase to the PAA/H₂O₂ treatment decreased the corrosion rates ofthe 1018 carbon steel by approximately 30-50% (FIG. 1). In deionizedwater the reduction in corrosion rates reached almost 60% (FIG. 2).

Example 2

An evaluation of friction reducer interference was conducted. Viscositymeasurements were obtained using a FANN Model 35 Viscometer. A total of600 ml of tap water containing a friction reducer was treated with 200ppm and 1000 ppm of peracetic acid with and without catalase. Themixture was blended for 15 seconds with a Hamilton Beach hand mixer andviscosity was measured at 300 rpm, room temperature. Viscosity valuesare reported in centipoise (cP).

Results. Table 1 shows the impact of PAA/H₂O₂ on friction reducerswithin a water source for oil/gas recovery, with and without theaddition of catalase. A negative effect of the PAA/H₂O₂ was observed onboth friction reducers. However, the effect was reduced in all casesfollowing treatment with catalase indicating the addition of catalase toremove H₂O₂ reduces any negative impact of PAA/H₂O₂ on the frictionreducers.

TABLE 1 With Read- Read- (Yes)/ ing ing Friction Without before afterBiocide Reducer (NO) chemi- chemi- Differ- dosage (1 gpt) catalase calcal ence PAA/H₂O₂  200 ppm FR#1 No 5.5 4.5  −1    PAA/H₂O₂  200 ppm FR#1Yes 5   4.25 −0.75 PAA/H₂O₂  200 ppm FR#2 No 3   2.5  −0.5  PAA/H₂O₂ 200 ppm FR#2 Yes 2.75 2.5  −0.25 PAA/H₂O₂ 1000 ppm FR#1 No 5.5  2.75−2.75 PAA/H₂O₂ 1000 ppm FR#1 Yes 5   2.75 −2.75 PAA/H₂O₂ 1000 ppm FR#2No 3   2.25 −0.75 PAA/H₂O₂ 1000 ppm FR#2 Yes 2.75 2.75 0  

Example 3

The impact of water pretreatment with 500 ppm of the EnviroSan product(75 ppm POAA) on micro efficacy in various fracking water mixtures wereevaluated. The example represents a baseline data set of various watertreatment options according to the invention. Table 2 and FIG. 3 showthe average log reduction in various slick water treatments with varyingppm PAA (without any catalase treatment or pretreatment), representing abaseline data set.

TABLE 2 Holding Percentage Avg. Log₁₀ Tank Reuse Slick Water ReductionPretreatment H₂O Treatment 2.5 minutes 5 minutes None  0% 22 ppm NO 5.535.75 POAA Catalase 75 ppm PAA 10% 29 ppm NO 6.45 6.71 POAA Catalase None36 ppm 4.32 4.72 POAA 75 ppm PAA 20% 47 ppm NO 6.42 6.55 PAA CatalaseNone 86 ppm 4.57 4.64 POAA 75 ppm PAA 30% 86 ppm NO 6.47 6.41 POAACatalase None 138 ppm  4.12 5.00 POAA

FIG. 3 shows the increasing amount of POAA required in tested watersamples having increased amounts of produced water (e.g. reused water).

Example 4

Planktonic kill studies were performed as an evaluation of biocideefficiency for PAA/H₂O₂ and PAA/H₂O₂/Catalase applications. Briefly,produced water samples were used to test the kill efficiency of PAA/H₂O₂at the following dosages: 25, 50, 75, 150 and 300 ppm PAA. Concentrationof catalase was fixed at 1000 ppm. The contact time was set to 10 and 60minutes. After contact time, bacterial enumeration was performed usingATP quantification assay. Bacterial enumeration was calculated at theend of the appropriate time and biocide efficacy determined bycomparison to an untreated sample.

Results. Planktonic kill studies demonstrate the addition of catalaseincreased microbial kill efficiency (FIGS. 4 and 5). For low dosageapplication of PAA/H₂O₂ (25 ppm), the addition of 1000 ppm of catalaseincreased the biocide efficiency by 48% after 10 minutes of treatment(23% after 60 minutes). The data from FIGS. 4 and 5 are also shown inTables 3A and 3B (respectively).

TABLE 3A (10 minute contact) % Reduction compared to % Reductioncompared to Dosage (ppm) blank (PAA/H2O2) blank (PAA/H2O2/catalase) 2532.7 80.8 75 71.2 82.1 100 80.5 85.5 300 82 88.1 750 85.3 97.6

TABLE 3B (60 minute contact) % Reduction compared to % Reductioncompared to Dosage (ppm) blank (PAA/H2O2) blank (PAA/H2O2/catalase) 2566.6 89.6 75 90.8 92.8 100 91.6 94 300 92.4 98.4 750 93.4 99.3

Example 5

Additional biocide testing was completed to assess the use of peracidand catalase compositions for water treatments used in oil fracking. Theuse of the commercially-available approximately 15 wt-% peracid (POAA)composition EnviroSan (Ecolab, Inc., St. Paul, Minn.) with and withoutcatalase was evaluated for biocide efficacy in water treatments for oilfracking. In particular, an EnviroSan stock solution (approximately 1400ppm POAA) with and without catalase was evaluated.

EnviroSan stock solutions with catalase were prepared as follows: 1 gramof EnviroSan (POAA) was added to 99 gram of deionized water in a beaker.With stirring, 100 μl of Optimase CA 400 L (catalase) was added througha syringe, and the stirring was continued for another 6.5 minutes. Thesubsequent assay (QATM 317) indicates that the resulting solutioncontains ˜1400 ppm peracetic acid, and no detectable H₂O₂. The stocksolution of EnviroSan with catalase is stable for at least 30 minuteswithout detectable changes on the level of POAA and/or H₂O₂.

A test system of Pseudomonas aeruginosa (ATCC 15442) and natural waterbacterial populations was employed. P. aeruginosa were inoculated atambient (18-22° C.) temperature using tryptone glucose extract (TGE)agar plating media and incubated at 35° C. for 48 hours.

Water mixtures as outlined in Table 3A were provided (showing thepercentage of 100 mL of each water sample type). The various testsubstances and the amount of chemistry added to 10 mL of inoculatedwater sample to achieve 20 ppm residual POAA after 5 minutes within thewater mixture are shown in Table 4B.

TABLE 4A Water Type A B C* D E* F G* Fresh 100% 90% 90% 80% 80% 70% 70%Produced 10% 10% 20% 20% 30% 30% *Solutions pretreated with 300 ppmEnviroSan more than 24 hours before micro evaluation

TABLE 4B Water Type A B C* D E* F G* Vol. 1701 μL 320 μL 320 μL 600 μL600 μL 960 μL 960 μL 1% Stock ppm 25 ppm 46 ppm 46 ppm 87 ppm 87 ppm 140ppm 140 ppm POAA

Testing methods. Prior (24 hours) to micro testing, water mixtures C, Eand G were mixed and pretreated with 300 ppm EnviroSan. Water sampleswere dispensed into sterile 250 mL Erlenmeyer flasks according to Table4A, ensuring each flask contained 100 mL total of test water and mixedwater types were completely homogeneous. Test water mixture wasdispensed (24.75 mL) into a centrifuge tube and 0.25 mL of a 10⁸ CFU/mLculture of P. aeruginosa was added and mixed thoroughly. 1 mL ofinoculated water mixture was serial diluted in PBDW. 10 mL of theinoculated water mixture was dispensed into 2 individual test tubes,where the appropriate volume of the EnviroSan solution with or withoutcatalase (Table 4B) was added to achieve 20 ppm POAA residual to eachtest tube in timed intervals and mixed. The methods of Example 5 wereemployed to make the EnviroSan with catalase stock solutions. Thenneutralized 1 mL samples in 9 mL of 0.5% sodium thiosulfate wereobtained after 2.5 minutes, as well as 5 minutes.

Results. Aerobic bacterial populations (CFU/mL) present in water samplemixtures (both not pretreated and pretreated with 300 ppm EnviroSan)after inoculation with a P. aeruginosa culture, as well as survivorspresent 2.5 minutes and 5 minutes after the addition of EnviroSanPOAA±catalase were evaluated as shown in Table 5.

TABLE 5 Water Av. Sample Test Exposure Log₁₀ Log₁₀ Log₁₀ Type SubstanceTime CFU/mL Growth Growth Reduction 100% Fresh After 6.90E+06 6.84 6.84Inoculation EnviroSan 2.5 minutes 1.00E+01 1.00 1.00 5.84 25 ppm POAA  5 minutes 8.00E+01 1.90 1.90 4.94  15 minutes 6.00E+01 1.78 1.78 5.06 30 minutes 2.00E+01 1.30 1.30 5.54 EnviroSan 2.5 minutes 7.00E+01 1.851.85 4.99 25 ppm POAA +   5 minutes 4.00E+01 1.60 1.60 5.24 Catalase  15minutes 3.00E+01 1.48 1.48 5.36  30 minutes 2.00E+01 1.30 1.30 5.54 90%Fresh/ After 1.05E+07 7.02 7.02 10% Inoculation Produced EnviroSan 2.5minutes 1.00E+01 1.00 1.00 6.02 46 ppm POAA 1.00E+01 1.00   5 minutes3.00E+01 1.48 1.24 5.78 1.00E+01 1.00 After 6.90E+06 6.84 6.84Inoculation EnviroSan 2.5 minutes 1.00E+01 1.00 1.00 6.02 46 ppm POAA +1.00E+01 1.00 Catalase   5 minutes 2.00E+01 1.30 1.15 5.87 1.00E+01 1.0090/10 After 1.03E+07 7.01 7.01 24 hour Inoculation PretreatmentEnviroSan 2.5 minutes 4.00E+01 1.60 1.45 5.56 by 300 ppm 46 ppm POAA2.00E+01 1.30 EnviroSan   5 minutes 1.00E+01 1.00 1.00 6.01 Product1.00E+01 1.00 80% Fresh/ After 1.00E+06 6.00 6.00 20% InoculationProduced EnviroSan 2.5 minutes 1.00E+01 1.00 1.50 4.50 87 ppm POAA1.00E+02 2.00   5 minutes 6.00E+01 1.78 1.74 4.26 5.00E+01 1.70 After1.00E+06 6.00 6.00 Inoculation EnviroSan 2.5 minutes 4.00E+01 1.60 1.304.70 87 ppm POAA + 1.00E+01 1.00 Catalase   5 minutes 4.00E+01 1.60 1.694.31 6.00E+01 1.78 80/20 After 1.00E+06 6.00 6.00 24 hour InoculationPretreatment EnviroSan 2.5 minutes 2.00E+01 1.30 1.15 4.85 by 300 ppm 87ppm POAA 1.00E+01 1.00 EnviroSan   5 minutes 2.00E+01 1.30 1.15 4.85Product 1.00E+01 1.00 70% Fresh/ After 5.90E+06 6.77 6.77 30%Inoculation Produced EnviroSan 2.5 minutes 5.00E+01 1.70 1.77 5.00 140ppm 7.00E+01 1.85 POAA   5 minutes 5.00E+01 1.70 1.70 5.07 5.00E+01 1.70After 6.00E+05 5.78 5.78 Inoculation EnviroSan 2.5 minutes 2.00E+01 1.301.50 5.27 140 ppm 5.00E+01 1.70 POAA +   5 minutes 4.00E+01 1.60 1.305.47 Catalase 1.00E+01 1.00 70/30 After 1.22E+07 7.09 7.09 24 hourInoculation Pretreatment EnviroSan 2.5 minutes 1.00E+01 1.00 1.00 6.09by 300 ppm 140 ppm 1.00E+01 1.00 EnviroSan POAA   5 minutes 1.00E+011.00 1.00 6.09 Product 1.00E+01 1.00

The average log reduction generated after a 2.5 minute exposure is shown(FIG. 6) at varying concentrations of POAA required to achieve 20 ppmresidual POAA after 5 minutes within its respective fracking watermixture. Across all tested fracking water mixtures, there does notappear to be a consistent trend to indicate that there are significantdifferences in efficacy generated between treatment of mixtures withPOAA alone vs. POAA+catalase. The results indicate there is not asignificant difference in bacterial reductions caused by pretreatment ofthe water mixtures 24 hours in advance with 300 ppm EnviroSan product,demonstrating the reduction of hydrogen peroxide with the catalase doesnot negatively impact micro efficacy.

Without being limited to a theory of the invention, it is likely thedosing of POAA chemistry is sufficiently high to generate significantkill by itself, without the potential benefits of water pretreatment orEnviroSan pre-reduction by catalase.

Example 6

Additional microbial testing was conducted to evaluate whether frackingwaters treated with EnviroSan (POAA) pre-reduced with catalase (as shownin Example 5 to have significantly reduced consumption of POAA) resultin improved micro efficacy. To evaluate improvements in micro efficacy,all water mixtures were treated with the same initial concentration ofPOAA EnviroSan (30 or 40 ppm) plus catalase, instead of aiming for aresidual POAA level and adjusting initial dosing according to the amountof produced water present.

The test systems (P. aeruginosa and natural water) described in Example5 were utilized. Water mixtures as outlined in Table 6 were provided(showing the percentage of 100 mL of each water sample type).

TABLE 6 Water Type A B C D Fresh 100% 90% 80% 70% Produced 10% 20% 30%

Water samples were dispensed into sterile 250 mL Erlenmeyer flasksaccording to Table 6, ensuring each flask contained 100 mL total of testwater and mixed water types were completely homogeneous. 50 mL was savedfor titration and 50 mL was used for micro evaluation. Test watermixture was dispensed (24.75 mL) into a centrifuge tube and 0.25 mL of a10⁸ CFU/mL culture of P. aeruginosa was added and mixed thoroughly. 1 mLof inoculated water mixture was serial diluted in PBDW. 10 mL of theinoculated water mixture was dispensed into 2 individual test tubes,where the appropriate volume of the EnviroSan 1 stock solution withcatalase was added to achieve 30 ppm or 40 ppm POAA to each test tube intimed intervals and mixed. The methods of Example 5 were employed tomake the EnviroSan with catalase stock solutions. Then neutralized 1 mLsamples in 9 mL of 0.5% sodium thiosulfate were obtained after 2.5minutes, as well as 5 minutes. Results: Table 7 shows the summary ofaerobic bacterial population (CFU/mL) present in water sample mixturesbefore and after inoculation with a P. aeruginosa culture, as well assurvivors present 2.5 minutes and 5 minutes after the addition of 30 ppmor 40 ppm POAA+catalase. In addition, the bottom portion of the tablesummarizes data for the treatment of inoculated fresh water with 30 ppmand 40 ppm POAA alone as a comparison to those pre-reduced withcatalase.

TABLE 7 Water Sample Test Exposure Log₁₀ Av. Log₁₀ Log₁₀ Type SubstanceTime CFU/mL Growth Growth Reduction Fresh Before 1.02E+03 3.01 3.01 PondInoculation Water After 1.01E+08 8.00 8.00 Inoculation EnviroSan 2.53.80E+04 4.58 4.31 3.69 30 ppm minutes 1.10E+04 4.04 POAA + 5 minutes2.04E+03 3.31 2.46 5.55 Catalase 4.00E+01 1.60 EnviroSan 2.5 1.00E+044.00 4.53 3.47 40 ppm minutes 1.15E+05 5.06 POAA + 5 minutes 2.00E+011.30 1.15 6.85 Catalase 1.00E+01 1.00 90 Fresh/ Before 1.10E+05 5.045.04 10 Inoculation Produced After 9.90E+07 8.00 8.00 InoculationEnviroSan 2.5 6.00E+03 3.78 2.74 5.26 30 ppm minutes 5.00E+01 1.70POAA + 5 minutes 1.00E+01 1.00 1.70 6.30 Catalase 2.50E+02 2.40EnviroSan 2.5 1.37E+03 3.14 2.91 5.08 40 ppm minutes 4.90E+02 2.69POAA + 5 minutes 6.00E+01 1.78 1.78 6.22 Catalase 6.00E+01 1.78 80Fresh/20 Before 1.80E+05 5.26 5.26 minutes Inoculation Produced After8.50E+07 7.93 7.93 Inoculation EnviroSan 2.5 4.00E+02 2.60 2.22 5.71 30ppm minutes 7.00E+01 1.85 POAA + 5 minutes 2.60E+02 2.41 1.71 6.22Catalase 1.00E+01 1.00 EnviroSan 2.5 1.00E+01 1.00 1.35 6.58 40 ppmminutes 5.00E+01 1.70 POAA + 5 minutes 6.00E+01 1.78 1.39 6.54 Catalase1.00E+01 1.00 70 Fresh/ Before 2.30E+05 5.36 5.36 30 InoculationProduced After 9.50E+07 7.98 7.98 Inoculation EnviroSan 2.5 1.00E+011.00 1.00 6.98 30 ppm minutes 1.00E+01 <1.00 POAA + 5 minutes 1.00E+01<1.00 <1.00 >6.98 Catalase 1.00E+01 <1.00 EnviroSan 2.5 1.00E+01 1.001.00 6.98 40 ppm minutes 1.00E+01 1.00 POAA + 5 minutes 2.00E+01 1.301.39 6.59 Catalase 3.00E+01 1.48 Fresh Before 1.02E+03 3.01 3.01 PondInoculation Water After 1.01E+08 8.00 8.00 Inoculation EnviroSan 2.52.35E+03 3.37 3.85 4.16 30 ppm minutes 2.10E+04 4.32 POAA 5 minutes8.00E+01 1.90 1.93 6.08 9.00E+01 1.95 EnviroSan 2.5 2.00E+04 4.30 3.974.04 40 ppm minutes 4.32E+03 3.64 POAA 5 minutes 1.20E+02 2.08 1.78 6.233.00E+01 1.48

Titration data showing POAA consumption was also analyzed and shown inTable 8. The titration data indicates the addition of catalase to theEnviroSan test substance significantly lowers the degradation rate ofPOAA within the water mixture over 5 minutes as compared to equivalentdosing of chemistry not pre-reduced with catalase.

TABLE 8 Actual Titrated Concentration (ppm POAA) Water Mixture DesiredConcentration 1 minute 5 minutes 100% Fresh 30 ppm POAA + 25 ppm 27 ppmCatalase 40 ppm POAA + 35 ppm 36 ppm Catalase 90% Fresh/10% 30 ppmPOAA + 26 ppm 27 ppm Produced Catalase 40 ppm POAA + 34 ppm 36 ppmCatalase 30 ppm POAA 21 ppm  8 ppm 40 ppm POAA 30 ppm 16 ppm 80%Fresh/20% 30 ppm POAA + 23 ppm 24 ppm Produced Catalase 40 ppm POAA + 31ppm 33 ppm Catalase 30 ppm POAA 13 ppm  0 ppm 40 ppm POAA 21 ppm  2 ppm70% Fresh/30% 30 ppm POAA + 24 ppm 42 ppm Produced Catalase 40 ppmPOAA + 18 ppm 33 ppm Catalase 30 ppm POAA  7 ppm  0 ppm 40 ppm POAA 12ppm  0 ppm

The average log reduction generated after a 2.5 minute exposure time to30 ppm or 40 ppm POAA EnviroSan with or without catalase in differentfracking water mixtures is shown in Table 8 and FIG. 7. The addition ofcatalase to the EnviroSan test substance appears to have no impact onefficacy generated against organisms present in the inoculated freshwater samples. The data also suggests that with increasing amounts ofproduced water within the tested water mixture, there is increasedefficacy generated within the 2.5 and 5 minute exposure times whentreated with EnviroSan pre-reduced with catalase.

Example 7

Additional micro efficacy performance was evaluated to confirm theimproved micro efficacy observed in Example 6 when using increasingamounts of produced water with the dosing static initial concentrationsof POAA (30 ppm or 40 ppm) with catalase. Improved micro efficacy withincreased amounts of produced water present in a mixture is a highlycounterintuitive result and was unexpected. Under normal conditions, itwould be expected to have decreased micro efficacy as the amount ofproduced water (e.g. recycled) increases and the amount of POAA remainsstatic as a result of the increased contamination found in producedwater as opposed to fresh water sources. As a result, subsequentevaluation observed the activity of the water itself against a spikedculture of P. aeruginosa over a 1 hour exposure period to determinewhether the produced water itself has an antimicrobial present.

All water mixtures were treated with an initial concentration of 30 ppmPOAA EnviroSan, both with and without the addition of catalase. The dataset evaluates whether there is a significant difference in microactivity generated between treatments of EnviroSan alone vs. EnviroSanpre-reduced with catalase.

All ratios of fracking water mixtures tested (100/0, 90/10, 80/20 &70/30) were freshly mixed solutions, as well as solutions mixed andpretreated with 500 ppm EnviroSan product more than 1 hour before thestart of the micro evaluation, in order to observe if a pretreatmentstep is of value for micro performance compared to those mixtures notpretreated. The test system (P. aeruginosa and natural water) describedin Example 5 was again utilized. Water mixtures as outlined in Table 9were provided (showing the percentage of 100 mL of each water sampletype).

TABLE 9 Water Type A B C* D E* F G* Fresh 100% 90% 90% 80% 80% 70% 70%Produced 10% 10% 20% 20% 30% 30% *Solutions pretreated with 500 ppmEnviroSan more than1 hour before micro evaluation.

The testing methods of Example 5 were utilized for the chemicallytreated water samples, differing only in the combination of the 10 mLinoculated water mixtures with appropriate volumes of the EnviroSan withor without catalase to achieve 30 ppm POAA residual to each test tube intimed intervals and mixed. The methods of Example 5 were employed tomake the EnviroSan with catalase stock solutions. In comparison, for thewater samples that were not chemically treated, 9.9 mL of test watermixture was dispensed into 2 individual test tubes. 0.10 mL of anapproximate 10⁸ CFU/mL culture of P. aeruginosa was added in timedintervals and mixed thoroughly. Then 1 mL samples were neutralized in 9mL of 0.5% sodium thiosulfate, followed by serial dilution andenumeration after 2.5 minutes, 5 minutes and 60 minute exposure times.

Table 10 shows a summary of aerobic bacterial population (CFU/mL)present in the water sample mixtures (both not pretreated and pretreatedwith 500 ppm EnviroSan) before and after inoculation with a P.aeruginosa culture, as well as survivors present 2.5 minutes and 5minutes after the addition of 30 ppm POAA with or without catalase. Inaddition, data for enumeration of water samples for antimicrobialactivity against P. aeruginosa over 60 minutes exposure are alsosummarized in Table 10.

TABLE 10 Water Av. Sample Exposure Log₁₀ Log₁₀ Log₁₀ Type Test SubstanceTime CFU/mL Growth Growth Reduction Pseudomonas aeruginosa ATCC 15442Fresh Before 3.10E+04 4.49 4.49 Pond Inoculation Water After 7.30E+077.86 7.92 Inoculation 9.50E+07 7.98 EnviroSan 2.5 minutes 1.99E+03 3.303.30 4.62 30 ppm POAA +   5 minutes 5.00E+01 1.70 1.70 6.22 CatalaseEnviroSan 2.5 minutes 1.90E+03 3.28 3.28 4.64 30 ppm POAA   5 minutes4.40E+01 1.64 1.64 6.28 No Chemical 2.5 minutes 5.24E+07 7.72 7.72 0.20Treatment   5 minutes 4.28E+07 7.63 7.63 0.29  60 minutes 5.64E+07 7.757.75 0.17 90 Fresh/ Before 1.22E+04 4.09 4.09 10 Inoculation ProducedAfter 7.10E+07 7.85 7.80 Inoculation 5.70E+07 7.76 EnviroSan 2.5 minutes3.30E+02 2.52 2.52 5.29 30 ppm POAA +   5 minutes 7.00E+01 1.85 1.855.96 Catalase EnviroSan 2.5 minutes 5.30E+04 4.72 4.72 3.08 30 ppm POAA  5 minutes 8.00E+03 3.90 3.90 3.90 No Chemical 2.5 minutes 5.56E+077.75 7.75 0.06 Treatment   5 minutes 5.04E+07 7.70 7.70 0.10  60 minutes5.24E+07 7.72 7.72 0.08 90 Fresh/ Before 1.20E+01 1.08 1.08 10Inoculation Produced After 6.70E+07 7.83 7.85 Pretreated Inoculation7.60E+07 7.88 with EnviroSan 2.5 minutes 6.00E+01 1.78 1.78 6.08 500 ppm30 ppm POAA +   5 minutes 5.00E+01 1.70 1.70 6.15 EnviroSan CatalaseEnviroSan 2.5 minutes 6.00E+01 1.78 1.78 6.08 30 ppm POAA   5 minutes3.00E+01 1.48 1.48 6.38 80 Fresh/ Before 1.39E+04 4.14 4.14 20Inoculation Produced After 6.50E+07 7.81 7.84 Inoculation 7.20E+07 7.86EnviroSan 2.5 minutes 1.30E+02 2.11 2.11 5.72 30 ppm POAA +   5 minutes3.00E+01 1.48 1.48 6.36 Catalase EnviroSan 2.5 minutes 4.48E+05 5.655.65 2.18 30 ppm POAA   5 minutes 2.86E+05 5.46 5.46 2.38 No Chemical2.5 minutes 5.00E+07 7.70 7.70 0.14 Treatment   5 minutes 5.32E+07 7.737.73 0.11  60 minutes 4.64E+07 7.67 7.67 0.17 80 Fresh/ Before 2.50E+011.40 1.40 20 Inoculation Produced After 5.70E+07 7.76 7.82 PretreatedInoculation 7.70E+07 7.89 with EnviroSan 2.5 minutes 5.00E+01 1.70 1.706.12 500 ppm 30 ppm POAA +   5 minutes 4.00E+01 1.60 1.60 6.22 EnviroSanCatalase EnviroSan 2.5 minutes 1.50E+03 3.18 3.18 4.65 30 ppm POAA   5minutes 6.00E+01 1.78 1.78 6.04 70 Fresh/ Before 1.61E+04 4.21 4.21 30Inoculation Produced After 6.70E+07 7.83 7.83 Inoculation 6.90E+07 7.84EnviroSan 2.5 minutes 3.40E+02 2.53 2.53 5.30 30 ppm POAA +   5 minutes7.00E+01 1.85 1.85 5.99 Catalase EnviroSan 2.5 minutes 9.00E+05 5.955.95 1.88 30 ppm POAA   5 minutes 8.00E+05 5.90 5.90 1.93 No Chemical2.5 minutes 5.48E+07 7.74 7.74 0.09 Treatment   5 minutes 4.56E+07 7.667.66 0.17  60 minutes 4.72E+07 7.67 7.67 0.16 70 Fresh/ Before 4.10E+011.61 1.61 30 Inoculation Produced After 6.40E+07 7.81 7.82 PretreatedInoculation 6.90E+07 7.84 with EnviroSan 2.5 minutes 9.60E+02 2.98 2.984.84 500 ppm 30 ppm POAA +   5 minutes 7.50E+02 2.88 2.88 4.95 EnviroSanCatalase EnviroSan 2.5 minutes 1.30E+04 4.11 4.11 3.71 30 ppm POAA   5minutes 5.64E+03 3.75 3.75 4.07 Sterile DI No Chemical 2.5 minutes5.52E+07 7.74 7.74 Water Treatment   5 minutes 5.84E+07 7.77 7.77  60minutes 5.16E+07 7.71 7.71

The water sample mixtures according to this study are summarized inTables 11A-B, showing the water sample mixtures and chemical treatments(Table 10A) and the titrated concentrations of POAA (Table 11B).

TABLE 11A Water Sample Mixture Treatment C1 80/20 Pretreated with 500ppm 30 ppm POAA EnviroSan EnviroSan ≥ 1 hour before study C2 80/20 30ppm POAA EnviroSan + Catalase C3 80/20 30 ppm POAA EnviroSan C4 80/20 NoChemical Treatment

TABLE 11B Titrated Concentration (ppm POAA) Test Solution 0 minutes 1minute 5 minutes C1 30 ppm 22 ppm 9 ppm C2 30 ppm 26 ppm 24 ppm  C3 30ppm 14 ppm 0 ppm C4  0 ppm  0 ppm 0 ppm

The titration data confirms that the addition of catalase to theEnviroSan test substance significantly lowers the degradation rate ofPOAA within the water mixture over 5 minutes as compared to equivalentdosing of chemistry not pre-reduced with catalase. In addition, waterpretreated with H₂O₂ 1 hour prior to testing slightly reduces POAAdegradation, as well, however not nearly as significantly as usingpre-reduced EnviroSan by catalase as the test substance.

Table 11C show the use of 30 ppm POAA with/without catalase treatmentcompared for micro performance at both 2.5 and 5.0 minutes exposuretimes. Upon addition of 10-30% reuse water a defined drop inantimicrobial performance was observed over both 2.5 and 5 minutes asperacid was rapidly consumed if not pretreated with catalase. A residualof 30 ppm POAA at 5 minutes was needed to achieve the desiredantimicrobial performance.

TABLE 11C Holding Avg. Log₁₀ Tank Percentage Slick Water ReductionPretreatment Reuse H₂O Treatment 2.5 minutes 5 minutes None  0% 30 ppmCatalase 4.62 6.22 PAA NO 4.64 6.32 Catalase None 10% 30 ppm Catalase5.29 5.96 PAA NO 3.09 3.91 Catalase None 20% 30 ppm Catalase 5.73 6.36PAA NO 2.19 2.38 Catalase None 30% 30 ppm Catalase 5.30 5.98 PAA NO 1.881.93 Catalase

Data showed that in the absence of reuse water (contaminated water) at30 ppm POAA with/without catalase treatment both achieved desiredantimicrobial performance. FIGS. 9 and 10 confirm the findings of nodifference in micro efficacy between fresh water samples treated with 30ppm POAA alone vs. 30 ppm POAA+catalase at 2.5 minutes (FIG. 9) and 5minutes (FIG. 10). It is thought that the use of fresh water does notinterfere with the stability of the POAA and therefore the microefficacy of the POAA in solution of fresh waters.

The data confirm there is a significant difference in activity generatedby POAA vs. POAA+catalase in tested water mixtures containing producedwater. On average, there was at least a 2 log greater reduction observedfor samples treated with POAA+catalase, than samples treated with POAAalone at the same time point (FIG. 11). This confirms the enhanced POAAstability and concomitant micro efficacy in reuse waters with reducedhydrogen peroxide.

However, with the pretreatment of water mixtures by 500 ppm EnviroSanmore than 1 hour prior to testing, the differences in efficacy observedbetween POAA alone vs. POAA+catalase treatments were eliminated (FIG.12). The log survivors present 2.5, 5 and 60 minutes after the additionof a P. aeruginosa culture into different mixtures of fracking waterwere nearly equivalent with the pretreatment of at least an hour beforetesting, thus confirming the water alone does not have any antimicrobialproperties.

Example 8

A micro efficacy comparison of POAA added at levels to target 30 ppmPOAA residuals at 5 minutes versus POAA pretreated with catalase wasconducted as set forth in Table 12.

TABLE 12 Holding Avg. Log₁₀ Tank Percentage Slick Water ReductionTreatment Reuse H₂O Treatment 2.5 minutes 5 minutes None 10% 30 ppmCatalase 5.29 5.96 PAA 46 ppm NO 4.32 4.72 PAA Catalase None 20% 30 ppmCatalase 5.73 6.36 PAA 86 ppm NO 4.57 4.64 PAA Catalase None 30% 30 ppmCatalase 5.30 5.98 PAA 138 ppm  NO 4.12 5.00 PAA Catalase

This data further confirms there is an improvement in the micro efficacyof POAA treated with catalase as opposed to POAA alone in all testedwater mixtures containing at least 10% produced water. (FIG. 13). Thisconfirms the enhanced POAA stability and concomitant micro efficacy inreuse waters with reduced hydrogen peroxide.

Example 9

The impact of peracid to hydrogen peroxide ratio on the stability of theperacid in produced waters was evaluated. Various commercially availableperacid use solutions were employed having the peracid to hydrogenperoxide ratios set forth in Table 13. FIG. 14 shows the increased ratioof peracid to hydrogen peroxide improves peracid stability.

TABLE 13 Sample Time (1) POAA/H₂O₂ (2) POAA/H₂O₂ (3) POAA/H₂O₂ (min.)8.26 1.37 0.21 0 87 82 89 1 58 56 40 4 48 31 12 5 47 23 3 6 46 14 0

Example 10

The effect of catalase on the peracid stability within treated waterswas further evaluated. Water blends of 80/20 (80% fresh water/20%produced water) were employed to analyze the impact on various treatmentsequences set forth in Table 14.

TABLE 14 Req'd. Enviro Catalase San RM Theoretical POAA POAA POAA POAA(14.5% Conc Initial Meas'd. Meas'd. Meas'd. Meas'd. POAA, TreatmentWater (ppm): POAA at 1 min. at 4 min. at 5 min. at 6 min. ppm SequenceBlends CA 400 (ppm) (ppm) (ppm) (ppm) (ppm) w/w) Simult. 80/20 100 82 6661 65 58 566 Add NA 80/20 0 82 56 31 23 17 566 Simult. 80/20 10 82 63 3431 26 566 Add Pretreated 80/20 10 82 76 75 75 75 566

As shown in FIG. 15, the most stable peracid systems were pretreatedwith catalase prior to addition to the blended water sources. Use of 10×the catalase yielded inferior results in comparison to the pretreatmentwith catalase demonstrating a clear benefit to pretreatment according tothe invention when using blended compositions. The composition notcontaining catalase demonstrated rapid POAA degradation.

Due to the efficacious results shown in FIG. 15, the same methods wereused to further evaluate a pretreatment using a lower concentration ofthe catalase as shown in Table 15.

TABLE 15 Catalase Theoretical POAA POAA POAA POAA RM Conc InitialMeas'd. at Meas'd. Meas'd. Meas'd. Treatment Water (ppm): POAA 1 min. at4 min. at 5 min. at 6 min. Sequence Blends CA 400 (ppm) (ppm) (ppm)(ppm) (ppm) Simult. 80/20 100 82 66 61 65 58 Add NA 80/20 0 82 56 31 2317 Simult. 80/20 10 82 63 34 31 26 Add Pretreated 80/20 5.8 82 76 75 7575

As shown in FIG. 16, the decreased catalase used in the pretreatedperacid composition again outperformed the simultaneous addition ofcatalase to a peracid system and/or no catalase system.

Example 11

The micro efficacy of a 30 ppm POAA (EnviroSan) composition, a 30 ppmPOAA (EnviroSan) with catalase composition and a 30 ppm mixed peraceticacid and peroctanoic acid peracid composition (POAA/POOA) were compared(FIG. 17). The micro efficacy was evaluated using 80% fresh water/20%produced water system from and oil- and gas-field operation.

The mixed POAA/POOA composition demonstrated improvements over use ofthe 30 ppm POAA composition alone. The same ppm peracid providedsignificantly improved results and therefore would enable use atsignificantly lower dosages, demonstrating synergy in a mixed peracidcomposition.

Example 12

The compatibility between peracetic acid and catalase compositions andcomponents of gel frac fluids were evaluated. The changes in viscosityof the gel fluid upon addition of peracetic acid with and withoutcatalase were evaluated. Linear guar slurries were initially prepared byhydration of guar polymers in standard 5-speed Waring blender. Deionizedwater was added and the mixture was stirred until a homogeneous mixturewas obtained. The linear gels were cross-linked in the presence ofborate based cross-linker activators and peracetic acid with and withoutcatalase. The viscosity of the fluids was subsequently monitored at 275°F. for 200 minutes using a Grace 5500 rheometer with a RIBS rotor-bobconfiguration.

The pass/fail criteria of the test were established as the fluidsmaintaining a minimum viscosity of 200 cP for 120 minutes at 275° F. Theresults shown in FIG. 18 demonstrate that varying concentrations ofperacetic acid between 1 ppm and 1000 ppm along with varyingconcentrations of catalase between 1 ppm and 200 ppm were tested. FIG.18 shows that hydrogen peroxide removal is critical for the viscosity ofthe gel to remain above 200 cP for the required time. Excess peraceticacid and hydrogen peroxide (e.g. insufficient catalase) in a systemfailed to sustain the viscosity above 200 cP for the required time.Testing could not be performed with peracetic acid and hydrogen peroxidealone (i.e. without catalase or other peroxide-reducing agent) as theproduct prevented a gel from being formed. This is considered a fail andwould not be compatible for field use.

Example 13

The concentration of peracid compositions was evaluated to determine theperoxide-reducing capability of enzymes. A catalase enzyme was evaluatedfor efficacy in reducing hydrogen peroxide at varying concentrationsunder increasingly concentrated peracid compositions. Thecommercially-available peracid (POAA) composition EnviroSan (Ecolab,Inc., St. Paul, Minn.) was evaluated using catalase enzymes added to 2%,3%, and 5% peracid compositions. The catalase enzymes were added to thePOAA solution and gently stirred under ambient conditions. After theaddition of catalase, the stirring was discontinued, and the sampleswere taken for iodometric assay.

As shown in Table 16, the peroxide-reducing enzymes demonstratedefficacy in removing hydrogen peroxide from the peracid composition atperacid levels as high as 3% POAA; however no impact was observed at thelevel of 5% POAA.

TABLE 16 2% POAA 3% POAA 3% POAA 5% POAA Time 1500 ppm 1500 ppm 2500 ppm1500 ppm (min.) Catalase Catalase Catalase Catalase 0 2.0% POAA 3.0%POAA 2.0% POAA 5.0% POAA 1.36% H2O2 2.04% H2O2 2.04% H2O2 3.40% H2O2 6.52.05% 2.97% POAA 2.99% POAA 4.96% POAA POAA 0.08% H2O2 0.33% H2O2 0.33%H2O2 3.81% H2O2 10 NA 2.83% POAA 2.95% POAA NA 0.23% H2O2 0.23% H2O2 15NA 2.95% POAA 2.87% POAA NA 0.21% H2O2 0.21% H2O3

Example 14

Differing processes of forming antimicrobial reduced peroxidecompositions according to embodiments of the invention were evaluated todetermine process effects on the peroxide-reducing capability ofenzymes. A first process (A) combined a peracid composition to asolution containing catalase enzyme. To 392 grams of DI water was added1.5 mL of ES 2000 catalase, then 107.37 grams of EnviroSan (POAA)peracid composition was slowly added to the solution during a period of5 minutes without stirring.

A second process (B) added a catalase composition to a diluted peracidcomposition. To the solution of 107.37 grams of EnviroSan (POAA) peracidcomposition in 392 grams of DI water, 0.5 mL of ES 2000 catalase wasadded during a period of 5 minutes without stirring.

As shown in Table 17, the process of adding the peroxide-reducingenzymes impacted the efficacy of the hydroxide removal from the POAAperacid compositions. As further shown in FIG. 19, the mixture of POAAand H₂O₂ is preferably added to the catalase solution to achieve themaximum efficiency of hydrogen peroxide removal/reduction.

TABLE 17 Time A B (min.) POAA % H2O2 % POAA % H2O2 % 0 3.00 2.24 3.002.24 10 3.01 0.46 3.12 2.22 20 3.01 0.46 3.06 2.26 45 3.30 0.32 2.992.17 60 2.96 0.48 3.02 2.13

Example 15

Field of use applications were analyzed to determine the amount of aperoxide-reducing enzyme necessary to obtain desired concentrations ofboth peracid and hydrogen peroxide in a treated water source. EnviroSan(POAA) peracid composition was added to water to reach the targeted POAAconcentrations set forth in Table 18, and the concentration of both POAAand H₂O₂ were confirmed by iodometric titration. Then catalase (ES2000)was added to the solution, and the sample was stored under ambientconditions. The concentration of POAA and H₂O₂ were monitored by theiodometric conditions.

As shown in Table 18, the pond water with POAA and H₂O₂ could be treatedwith as low as 0.5 ppm catalase within 4 hours. The results furtherdemonstrate that higher levels (concentrations) of catalase work moreefficiently in decomposing H₂O₂ from the peracid composition.Regardless, approximate 1 ppm catalase is sufficient for treating thewater source. In addition, the results show that under the testedambient conditions, catalase selectively decomposes the H₂O₂ withouthaving any negative impact on POAA stability.

TABLE 18 POAA Catalase (ppm) Time (hr). (ppm) H2O2(ppm) 0.5 0 14.6 12.00.5 1 15.0 7.5 0.5 2 14.3 6.5 0.5 3.6 14.2 1.8 0.5 0 31.1 22.8 0.5 132.0 12.2 0.5 2 29.2 7.8 0.5 3.6 30.6 3.4 1.0 0 14.8 12.6 1.0 1 14.6 3.71.0 2 14.2 1.1 1.0 3.6 15.9 0.4 1.0 0 30.1 23.3 1.0 1 31.0 7.6 1.0 229.6 2.3 1.0 3.6 29.3 0.0

Example 16

The stability of treated peracid compositions according to the inventionwas evaluated to determine the impact of acidulants on compositionalstability. pH adjustments to POAA compositions were made using variousacidulants to decrease the pH of the peracid compositions as a means ofpretreating the compositions prior to use according to the variousmethods of the invention. The EnviroSan (POAA) peracid composition waspretreated with the following materials to assess the impact on thestability of POAA: chlorine dioxide (ClO₂), catalase, or nitric acid(HNO₃). The following methods were employed to test the stability (asmeasured by remaining ppm POAA) of the peracid compositions in 20/80water (produced/5 grain water), as set forth in Table 19.

The chlorine dioxide (100 ppm) was added as a pretreatment to 100 ml of100% produced water. Two hours elapsed before the 1% EnviroSan was addedand POAA stability was tested in the acidified water source to betreated according to the invention.

The catalase pretreatment consisted of adding 1% EnviroSan to 100 ppmcatalase. The solution was stirred for 6.5 minutes before POAA stabilitywas tested.

The pretreatment of 100 ml of 100% produced water with the acid (dilutedHNO₃ to pH 2.5) included stirring the solution magnetically for ˜1 hour.Then 20 g of the acidified water to be treated according to theinvention was mixed with 80 g of 5 grain water, and the pH of thesolution was adjusted from 5.5 to 6.6 before adding the 1% EnviroSan forPOAA stability testing.

No acidification and/or pretreatment of the water source was conductedfor the Control experiment.

TABLE 19 Sample Time Catalase (min.) Control Pretreated ClO₂ Pretreated*Acid pretreated 0 27 27 28 28 1 14 22 28 26 4 3 20 29 19 5 2 19 28 22 60 20 29 22 *Minor interference observed in iodometric titration

As shown in FIG. 20, there is a clear benefit for use of an acidulantwith the treated peracid compositions according to the invention inorder to improve the peracid stability.

The improved stability (ppm POAA over elapsed time) shown demonstratesthat a pretreatment of a water source to decrease the pH of the water tobe acidic, results in prolonged peracid stability.

Example 17

To a water mixture of 80/20 (5 grain/produced water) was added thevarious peracid compositions with stirring. The level of peracid atspecific times was assayed by iodometric titration. The followingperacid compositions were employed: EnviroSan: 60 microliter/100 g(POAA, 13.97%, H₂O₂, 10.41%); Low Peroxide POAA: 65 microliter/100 g(POAA 12.72, H₂O₂, 1.55%); and EnviroSan/HAC (i.e. Acidified EnviroSan):60 microliter EnviroSan plus 25 microliter/Hac/100 g.

For catalase treatment, 0.3 g of ES 2000 was added to 78.53 g of water,then 21.47 g of EnviroSan was added in the solution without stirring. Atthe end of the addition the peracid and hydrogen peroxide concentrationswere assayed (POAA 2.77%, H₂O₂ 0.51%). The results are shown in Table20.

TABLE 20 Time POAA Sample (min.) W (g) V_((ml. 0.1 N Na2S2O3)) (ppm) pHEnviroSan 0 94 6.30 1 21.08 0.47 85 2 18.19 0.30 63 3 17.62 0.24 52 420.51 0.24 44 5 21.78 0.22 38 Low Peroxide 0 90 5.42 POAA 1 21.78 0.4884 2 22.36 0.48 82 3 18.95 0.4 80 4 19.61 0.42 81 5 18.11 0.39 82Envirosan-HAc (i.e. 0 94 5.38 acidified) 1 21.73 0.48 84 2 17.94 0.40 853 17.97 0.38 80 4 18.07 0.38 80 5 21.22 0.42 75 EnviroSan 0 90 6.18 (3%POAA)- 1 17.92 0.38 81 Catalase 2 17.96 0.34 72 3 18.5 0.32 66 4 19.750.31 60 5 23.97 0.36 57

Again as shown in FIG. 21, there is a clear benefit for use of anacidulant with the treated peracid compositions according to theinvention in order to improve the peracid stability.

Example 18

An inorganic metal peroxide-reducing agent was evaluated for itsspecificity of reducing hydrogen peroxide in peracid compositions incomparison to peracid reduction. As shown in Table 21, various POAAcompositions with varying starting concentrations of hydrogen peroxidewere contacted with a platinum (Pt) catalyst. The tested compositionswere generated as follows: Composition A (2000 ppm POAA plus 250 ppmH₂O₂; 0.2166% w/w peracid, 0.0034 wt-% measured H₂O₂); Composition B(2000 ppm POAA plus 500 ppm H₂O₂; 0.2166% w/w peracid, 0.0094 wt-%measured H₂O₂); Composition C (2000 ppm POAA plus 1000 ppm H₂O₂; 0.2138%w/w peracid, 0.0340 wt-% measured H₂O₂); Composition D (2000 ppm POAAplus 2000 ppm H₂O₂; 0.2119% w/w peracid, 0.0540 wt-% measured H₂O₂).

A zeolite (i.e. a porous structure that can accommodate a wide varietyof cations and are used in formulating catalysts) was used to suspendinga sample of an inorganic metal peroxide-reducing agent. The zeolite wassaturated with various metal peroxide-reducing agents (as set forth inthe various different examples) in a solution of peracetic acid. Thezeolites that were employed are commonly used in the industry ofhydrocarbon cracking for catalysis. The concentrations of POAA and H₂O₂were then measured with an iodometric titration over time to show theimpact of the particular metal peroxide-reducing agent on selective ornon-selective degradation of POAA and/or H₂O₂.

Table 21 shows the comparison of the initial POAA concentration and thefinal POAA concentration after 15 minutes contact with theperoxide-reducing agent according to the invention is shown in FIG. 22.

TABLE 21 Composition Peroxide Conc initial POAA 15 minute POAA A 34 21661862 B 94 2166 1606 C 340 2138 1188 D 540 2119 817

As shown in Table 22, the decomposition rates of the POAA concentrationin the various peracid compositions are further shown. As shown in bothTable 22 and FIG. 23, as the concentration of hydrogen peroxideincreases the POAA loss rate similarly increases. As a result, theperoxide-reducing agent provides a partially selective peroxidedecomposition from peracid compositions.

TABLE 22 ppm H₂O₂ POAA loss rate 34 −20.267 94 −37.333 340 −63.33 540−86.8

The results demonstrate the partial selectivity of the inorganicperoxide-reducing agent platinum (Pt), suitable for use according to themethods of the invention. The inorganic peroxide-reducing agent was thenevaluated in combination with the peroxide-reducing enzyme agentcatalase. The 2000 ppm POAA compositions were measured at 0 minutes, 30minutes, 60 minutes, 120 minutes and 240 minutes, as shown in Table 23under the various combinations with a catalase peroxide-reducing enzyme.

TABLE 23 POAA Concentration Catalase + Time Catalase + Pt Pretreated PtCatalase only 0 1934 1934 1934 30 1824 1784 1891 60 1710 1615 1929 1201406 1210 1877 240 874 608 1568

FIG. 24 graphically shows the results of the decrease in POAA (e.g.peracid decomposition), showing that inorganic peroxide-reducing agentresults in less selective hydrogen peroxide reduction or decompositionin comparison to the peroxide-reducing enzyme catalase. However, theinorganic peroxide-reducing agent provides a partially selectiveperoxide decomposition from peracid compositions.

Example 19

Additional inorganic metals were evaluated for use as solid catalystsfor evaluation as peroxide decomposition catalysts according to themethods of the invention. The metals tungsten (W), zirconium (Zr), andruthenium (Ru) were evaluated to determine whether the metalspreferentially reduce hydrogen peroxide concentration over peracidconcentration within a peracid composition. Table 24 shows the variousformulations evaluated over 4 hours.

TABLE 24 control WZr control WZr Time POAA POAA Ru POAA H₂O₂ H₂O₂ RuH₂O₂ 0 1986 1986 1986 1547 1547 1547 15 1938 2252 513 1539 1267 0 601862 1330 228 1556 1071 0 240 1539 190 38 1509 327 0

As shown in FIG. 25 the decrease in both POAA (e.g. peraciddecomposition) and hydrogen peroxide are compared. Both inorganicperoxide-reducing agents resulted in significant decrease in both POAAand hydrogen peroxide, showing only a slight preference in hydrogenperoxide decomposition over POAA.

Example 20

Various additional inorganic metals and metal compounds were furtherevaluated for use as peroxide decomposition catalysts (e.g.peroxide-reducing agents) according to the methods of the invention. Themetals were provided as solid catalysts to POAA solutions.

Table 25 shows the various solutions that were tested against 10 g CoMo,cobalt molybdenum peroxide-reducing agent sample, including a POAA pluscatalase peracid composition, hydrogen peroxide plus acetic acidcomposition, hydrogen peroxide composition.

TABLE 25 POAA Concentration H₂O₂ Concentration Equil. POAA + Time POAAPOAA + catalase Equil. POAA H₂O₂ H₂O₂_HOAc catalase 0 2014 2071 18361615 1572.5 0 15 570 136.8 54.4 1343 1462 68 30 45.6 106.4 0 1156 1351.56.8 45 0 0 0 994.5 1207 0 60 0 0 0 841.5 1062.5 0

As shown in FIGS. 26-27, the POAA loss (FIG. 26) and hydrogen peroxideloss (FIG. 27) are a function of time of exposure to theperoxide-reducing agent CoMo.

Table 26 shows the various solutions that were tested against 10 g NiW,a nickel wolfram inorganic peroxide-reducing agent sample, including aPOAA plus catalase peracid composition, hydrogen peroxide plus aceticacid composition, hydrogen peroxide composition.

TABLE 26 POAA Concentration H2O2 Concentration Equil. POAA + POAA POAA +Equil. Time POAA catalase Control catalase H₂O₂_HOAc H₂O₂ POAA Control 02071 2014 2014 0 1572.5 1615 1836 1572.5 15 1976 1919 1938 0 1589.5 15811836 1589.5 30 1862 1786 1900 34 1589.5 1598 1751 1615 45 1710 1672 188168 1606.5 1615 1700 1640.5 60 1406 1539 1843 68 1606.5 1615 1632 1666

As shown in FIGS. 28-29 POAA loss (FIG. 28) and hydrogen peroxide loss(FIG. 29) are a function of time in the presence of a NiWperoxide-reducing agent.

Table 27 shows the various solutions that were tested against 10 g NiMo,a nickel molybdenum inorganic peroxide-reducing agent sample, includinga POAA plus catalase peracid composition, hydrogen peroxide plus aceticacid composition, hydrogen peroxide composition.

TABLE 27 POAA Concentration H2O2 Concentration Equil. POAA + POAA POAA +Equil. Time POAA catalase Control catalase H₂O₂_HOAc H₂O₂ POAA Control 02071 2014 2014 0 1572.5 1615 1836 1572.5 15 1482 1254 1938 289 1589.51581 1377 1589.5 30 760 874 1900 450.5 1615 1555.5 1173 1615 45 1140 4561881 612 1640.5 1530 782 1640.5 60 0 532 1843 544 1666 1496 0 1666

As shown in FIGS. 30-31 POAA loss (FIG. 30) and hydrogen peroxide loss(FIG. 31) are a function of time in the presence of a NiMoperoxide-reducing agent.

Additional testing using the NiMo, nickel molybdenum inorganicperoxide-reducing agent was conducted using a different titrationmethodology, due to some molybdenum metal leaching into the POAAsolution (e.g. potentially negative effects on the POAA/hydrogenperoxide separation). To correct this, 2 separate 10 ml samples werecollected at each time point during the test. One of the samples wastreated with a small amount (˜1 mml) of added catalase to eliminate thehydrogen peroxide in the solution. The second solution was titrated fortotal oxygen content with addition of oxygen catalyst, sulfuric acid andKI. As a result, the titration volume from the catalase treated samplerepresents a direct measurement of the POAA content in the solution, andthe total oxygen titration minus the catalase treated titration equalsthe amount of peroxide in the solution. The results are outlined inTable 28 and shown in FIGS. 32-33.

TABLE 28 Titration Total with Oxygen ppm ppm POAA H₂O₂ time catalasetitration POAA H₂O₂ control control A 0 5.2 15.65 1976 1776.5 20141572.5 15 0.5 5.3 190 816 1938 1589.5 30 0.3 4.9 114 782 1900 1615 450.2 4.4 76 714 1881 1640.5 60 0.2 4.2 76 680 1843 1666 B (Pre-treatedPOAA with catalase) 0 5.3 5.3 2014 0 2014 0 15 0.2 2.4 76 374 1938 20 300.2 2.2 76 340 1900 40 45 0.08 1.9 30.4 309.4 1881 60 60 0.12 1.65 45.6260.1 1843 80

Table 29 shows the various solutions that were tested against 10 g Mo, amolybdenum inorganic peroxide-reducing agent sample, including a POAAplus catalase peracid composition, hydrogen peroxide plus acetic acidcomposition, hydrogen peroxide composition.

TABLE 29 POAA Concentration H₂O₂ Concentration Equil. POAA + POAA POAA +Equil. Time POAA catalase Control catalase H₂O₂_HOAc H₂O₂ POAA Control 02071 2014 2014 0 1572.5 1615 1836 1572.5 15 1482 988 1938 408 15301334.5 1615 1589.5 30 988 836 1900 493 1436.5 1181.5 1462 1615 45 684608 1881 569.5 1317.5 986 1088 1640.5 60 0 418 1843 654.5 1190 841.5 01666

As shown in FIGS. 34-35 POAA loss (FIG. 34) and hydrogen peroxide loss(FIG. 35) are a function of time in the presence of a Moperoxide-reducing agent.

Additional testing using the Mo, molybdenum inorganic peroxide-reducingagent was conducted using a different titration methodology, as outlinedabove with respect to the NiMo catalyst testing that was re-analyzed.The results are outlined in Table 30 and shown in FIGS. 36-37.

TABLE 30 Titration Total with Oxygen ppm ppm POAA H₂O₂ time catalasetitration POAA H₂O₂ control control A 0 5.4 14.85 2052 1606.5 20141572.5 15 2.55 6 969 586.5 1938 1589.5 30 0.12 1.3 45.6 200.6 1900 161545 0.08 1 30.4 156.4 1881 1640.5 60 0.08 0.72 30.4 108.8 1843 1666 B(Pre-treated POAA with catalase) 0 5.3 5.3 2014 0 2014 0 15 1.3 4.1 494476 1938 20 30 0.4 3.4 152 510 1900 40 45 0.2 3.2 76 510 1881 60 60 0.23.1 76 493 1843 80

Example 21

Micro efficacy of peracid compositions utilizing variousperoxide-reducing agents according to embodiments of the invention wasanalyzed, as shown in Table 31. The control sample was a contaminatedwater source from a field water composition used in the field ofhydraulic fracturing (i.e. 73,412,793.2 micro equivalents per gramcontaminants). Peracid samples with and without hypochlorite were addedto the Control contaminated water source and were tested to determineeffect on micro efficacy of the use of and sequencing of the potentialperoxide-reducing agent. As reference in this example, the POAA employedis a 15% peracetic acid and 10% hydrogen peroxide composition (such ascommercially-available as EnviroSan). As set forth in Tables 31-32, thereference to “X2” refers to a second sequence of dosing the POAA and/orHypochlorite to the Control contaminated water source. For example, afirst dose of 250 ppm POAA was added to treat the Control contaminatedwater source and thereafter a second dose was administered.

According to the Tables 31-32, the amount of active (ppm) POAA and/orhypochlorite in the Control treated water sources is as follows, forexample: 250 ppm POAA is equivalent to 37.5 ppm POAA in solution of theControl water source; 250 ppm hydrogen peroxide is equivalent to 25 ppmhydrogen peroxide in solution of the Control water source.

TABLE 31 ATP Sample Conc Volume (pg Micro % Sample RLU_(UC1) (mL)RLU_(cATP) ATP/g) Equivs/g) Reduction Control 11725 20 1721530 73412.873,412,793.2 Control with POAA 11725 10 5497 468.8 468,827.3 99% 250 ppm(X2) Control with Hypo 11725 10 38791 3308.4 3,308,400.9 95% 250 ppm(X2) Control with 11725 10 34071 2905.8 2,905,842.2 96% Hypo/POAA 250ppm each Control with 11725 10 25606 2183.9 2,183,880.6 97% POAA/Hypo250 ppm each Control with Hypo 11725 10 58401 4980.9 4,980,895.5 93% 500ppm Control with POAA 11725 10 24795 2114.7 2,114,712.2 97% 500 ppm

Additional evaluation of the process of using peroxide-reducing agentsin sequence was further analyzed as shown in Table 32 using additionalwater samples, including deionized water (i.e. not contaminated), andthe Control (as set forth above as a contaminated water source).

TABLE 32 POAA POAA NaOCl NaOCl H2O2 H2O2 Time ppm ppm ppm ppm ppm ppm %Samples (min) meas. calc. meas. calc. meas. calc. Reduction DI H2O withHypo 2 0.00 0 137.30 300 0.00 0 1000 ppm DI H2O with Hypo 2 0.00 0149.02 300 0.00 0 1000 ppm DI H2O with POAA 2 62.64 75 61.32 150 23.7850 500 ppm/Hypo 500 ppm DI H2O with POAA 2 69.54 75 68.07 150 31.95 50500 ppm/Hypo 500 ppm DI H2O with POAA 2 170.23 150 0.00 0 121.85 1001000 ppm Control with POAA 30 24.52 75 0.00 0 40.74 50 99.4% 250 ppm(X2) Control with Hypo 30 0.00 0 7.20 150 0.00 0 95.5% 250 ppm (X2)Control with 30 1.85 37.5 3.62 75 19.87 25 96.0% Hypo/POAA 250 ppm eachControl with 30 0.94 37.5 1.84 75 15.15 25 97.0% POAA/Hypo 250 ppm eachControl with Hypo 30 0.00 0 3.70 150 0.00 0 93.2% 500 ppm Control withPOAA 30 3.77 75 0.00 0 37.12 50 97.1% 500 ppm DI H2O with POAA 30 82.1275 0.00 0 66.80 50 250 ppm (X2) DI H2O with Hypo 30 0.00 0 81.84 1500.00 0 250 ppm (X2) DI H2O with 30 33.84 37.5 33.13 75 6.73 25 Hypo/POAA250 ppm each DI H2O with 30 35.90 37.5 35.15 75 6.76 25 POAA/Hypo 250ppm each

The results shown in Table 32 demonstrate that hypochlorite hasefficacious impact on the decomposition of hydrogen peroxide (in waternot containing any biological contamination). The mixed systems showedincreased peroxide decomposition compared to the non-mixed peracidsystems. This demonstrates the effect of biological contamination inwater competing with hydrogen peroxide decay by sodium hypochlorite.More rapid decomposition or decay of the peracetic acid and sodiumhypochlorite is observed in conjunction with increased microbialpercentage reduction while hydrogen peroxide shows increased stability.

The peracetic acid and sodium hypochlorite are indistinguishable intitration, and are therefore presumed to consist of ½ of the titrateablematerial; however the focus of the evaluation was solely on the hydrogenperoxide decomposition.

The inventions being thus described, it will be obvious that the samemay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the inventions and all suchmodifications are intended to be included within the scope of thefollowing claims.

What is claimed is:
 1. A method of treating oil or gas field operationwater sources comprising: treating a percarboxylic acid composition,wherein said percarboxylic acid composition comprising percarboxylicacid and hydrogen peroxide, with an inorganic peroxide-reducing agent togenerate an antimicrobial composition, wherein said inorganicperoxide-reducing agent is a hypohalite, and wherein said inorganicperoxide-reducing agent reduces hydrogen peroxide from saidpercarboxylic acid composition; providing the antimicrobial compositionto a water source in need of treatment, wherein said water source inneed of treatment is selected from the group consisting of drillingfluid water, a fracking water, and a produced water from an oil or gaswell, to form a treated water source, wherein the treated water sourcecomprises (i) from 0.5 ppm to 1000 ppm inorganic peroxide-reducingagent; (ii) from about 0 wt-% to about 1 wt-% of hydrogen peroxide;(iii) from about 0.0001 wt-% to about 10.0 wt-% of a C₁-C₂₂ carboxylicacid; and (iv) from about 0.0001 wt-% to about 10.0 wt-% of a C₁-C₂₂percarboxylic acid, wherein the hydrogen peroxide to percarboxylic acidratio is from about 0:100 to about 1:10 by weight; and directing thetreated water source into an oil or gas well or disposing of the treatedwater source.
 2. The method of claim 1, wherein the water source in needof treatment comprises produced water.
 3. The method of claim 2, whereinthe water source comprises at least 1 wt-% produced water.
 4. The methodof claim 1, wherein said hypohalite is hypochlorite.
 5. The method ofclaim 1, wherein the antimicrobial composition does not interfere withfriction reducers, viscosity enhancers, other functional ingredientsfound in the water source, or combinations thereof.
 6. The method ofclaim 1, wherein the percarboxylic acid stability is improved throughthe treating of the percarboxylic acid composition with the inorganicperoxide-reducing agent to minimize hydrogen peroxide concentrationwithin the percarboxylic acid composition, and wherein the concentrationof the C₁-C₂₂ carboxylic acid is from about 0.0001 wt-% to about 5.0wt-%, and wherein the concentration of the C₁-C₂₂ percarboxylic acid isfrom about 0.0001 wt-% to about 5.0 wt-%, and wherein hydrogen peroxideis from about 0 wt-% to about 0.5 wt-%.
 7. The method of claim 1,wherein the percarboxylic acid is peracetic acid and the carboxylic acidis acetic acid.
 8. The method of claim 1, wherein the method furthercomprises adding an acidulant to the water source in need of treatmentbefore the addition of the antimicrobial composition.
 9. A method oftreating oil or gas field operation water sources comprising: adding apercarboxylic acid composition, wherein said percarboxylic acidcomposition comprising percarboxylic acid and hydrogen peroxide, and aninorganic peroxide-reducing agent, wherein said inorganic peroxidereducing agent is a hypohalite, to a water source in need of treatment,wherein said water source in need of treatment is selected from thegroup consisting of drilling fluid water, a fracking water, and aproduced water from an oil or gas well, and reducing the hydrogenperoxide with the inorganic peroxide-reducing agent, to form a treatedwater source having a hydrogen peroxide to percarboxylic acid ratio fromabout 0:100 to about 1:10 by weight, wherein said treated water sourcecomprises (i) less than about 1000 ppm of the inorganicperoxide-reducing agent; (ii) from about 0 wt-% to about 1 wt-% hydrogenperoxide; (iii) from about 0.0001 wt-% to about 10.0 wt-% of a C₁-C₂₂carboxylic acid; and (iv) from about 0.0001 wt-% to about 10.0 wt-% of aC₁-C₂₂ percarboxylic acid; wherein the treated water source reducescorrosion caused by hydrogen peroxide and microbial-induced corrosion,and wherein the antimicrobial composition does not interfere withfriction reducers, viscosity enhancers, other functional ingredientsfound in the water source or combinations thereof.
 10. The method ofclaim 9, wherein the water source in need of treatment comprisesproduced water.
 11. The method of claim 10, wherein the water sourcecomprises at least 1 wt-% produced water.
 12. The method of claim 9,wherein the hypohalite is hypochlorite.
 13. The method of claim 9,further comprising the steps of directing the treated water source intoan oil or gas well or disposing of the treated water source.
 14. Themethod of claim 9, wherein said reducing the hydrogen peroxide with theinorganic peroxide-reducing agent improves the percarboxylic acidstability.
 15. The method of claim 9, wherein the percarboxylic acid isperacetic acid and the carboxylic acid is acetic acid.
 16. The method ofclaim 9, wherein the adding of the percarboxylic acid composition andthe peroxide-reducing agent to the water source occurs on an at leastevery 5 day dosing cycle.
 17. The method of claim 9, wherein the methodfurther comprises adding an acidulant to the water source in need oftreatment before the addition of the percarboxylic acid and inorganicperoxide-reducing agent.
 18. A method of treating oil or gas fieldoperation water sources comprising: forming a treated water source by(a) treating a percarboxylic acid composition, wherein saidpercarboxylic acid composition comprising percarboxylic acid andhydrogen peroxide, with an inorganic peroxide-reducing agent, whereinsaid inorganic peroxide-reducing agent is a hypohalite, to reduce thehydrogen peroxide in the percarboxylic acid composition, and generate anantimicrobial composition, then providing the antimicrobial compositionto a water source in need of treatment, wherein said water source inneed of treatment selected from the group consisting of drilling fluidwater, a fracking water, and a produced water from an oil or gas well,or (b) adding said percarboxylic acid composition and said inorganicperoxide-reducing agent to said water source in need of treatment, andreducing the hydrogen peroxide with the inorganic peroxide-reducingagent; wherein the treated water source comprises (i) from 0.5 ppm to1000 ppm inorganic peroxide-reducing agent, (ii) from about 0 wt-% toabout 1 wt-% of hydrogen peroxide; (iii) from about 0.0001 wt-% to about10.0 wt-% of a C₁-C₂₂ carboxylic acid; and (iv) from about 0.0001 wt-%to about 10.0 wt-% of a C₁-C₂₂ percarboxylic acid, wherein the hydrogenperoxide to percarboxylic acid ratio is from about 0:100 to about 1:10by weight; and directing the treated water source into an oil or gaswell or disposing of the treated water source, wherein the treated watersource reduces corrosion caused by hydrogen peroxide andmicrobial-induced corrosion, and does not interfere with frictionreducers, viscosity enhancers, or other functional ingredients found inthe water source.
 19. The method of claim 18, wherein the hypohalite ishypochlorite.
 20. The method of claim 18, wherein the percarboxylic acidis peracetic acid and the carboxylic acid is acetic acid.